Command PostJuly 13, 2007
Under Pressure
By Joe P. Sheehan

Jake Peavy has been a fantastic success so far this season. Using a fastball that sits in the high 90's, a slider that breaks in on right-handed hitters and a changeup that breaks the opposite direction, Peavy has dominated the National League. A more accurate statement would be that he dominated the National League in May, allowing only three earned runs in 34.0 innings pitched, with opponents hitting just .164 against him. Even outside of May, Peavy has done very well this season, so what can the Pitch f/x system tell us about him and his pitches?


Here's a chart showing Peavy's start on May 27th vs. the Brewers. He threw all four of his pitches in this start and you can see the different breaks that they have. His fastball and slider both break toward a right-handed hitter, while his changeup moves away from righties. His curve is a standard curve from a right-handed pitcher and runs away from a right-handed hitter. There really isn't anything particularly special in this chart, and I put it in to get a feel for his pitches. In this article I'm going to examine when during a game Peavy throws his pitches, and specifically, does he pitch differently in high pressure situations or low pressure situations?

Before I could look at when Peavy throws his pitches I needed to classify them. As I was classifying the pitches it appeared that he had five pitches. However, when I looked at data from individual games, I could only find evidence for four pitches, the fastball, slider, changeup and curveball. I was pretty confident that he only threw those four pitches, but there was clearly another group in the season graph.


This wasn't a case of stadium variation, as all these games were in San Diego, and they were all prior to June 4th, which was when began varying the "release point" distance. After another round of looking at the data from individual games, I found two problems. One was pitches that weren't classifiable. These pitches had similar movement to Peavy's fastball, but the velocity was much slower. I'm not sure what caused this, and I removed them from the data set, but it just serves as another reminder to be careful with these data. The second problem I ran into was that Peavy had some serious variation in how his pitches moved from start to start. This is pretty different from what I found in my last article, and I'm not sure what it means. There were some patterns where every pitch in certain starts varied the same amount, which would indicate a camera change, so the differences might just be another reminder to be careful. However, for the purposes of this article, variations between starts don't matter as long as each start is consistent with itself, which was the case for the starts I examined. I ended up using Peavy's starts from 4/30, 5/11, 5/16, 5/22, 5/27, 6/7 and 6/19. Here is a table showing the percentage of each pitch that Peavy throws overall.

Pitch         Total   Mix
Fastball      417     0.61
Slider        159     0.23
Changeup      98      0.14
Curveball     11      0.02
Total         685     1.00

The chart is very basic, but one thing that stuck out to me was that Peavy throws his fastball 61% of the time, which initially seemed like a lot of fastballs. However, after comparing him to other hard throwing right-handers, such as Josh Beckett (61% fastballs) and Justin Verlander (65% fastballs), 61% seems about right. How often does Peavy rely on his fastball when the pressure is on though?

Once I had all Peavy's pitches classified I matched them to the Leverage Index that they were thrown in. I assigned the Leverage Index (LI) at the beginning of a plate appearance to any pitch thrown during that plate appearance, with steals and other runner advancements during the play being accounted for. I split up Peavy's pitches into those that he threw when the LI was greater than one and when it was less than or equal to one. One is defined as average LI, so I'm splitting Peavy's pitches into above average (high) pressure situations and below average (low) pressure situations. Here are Peavy's LI splits according to his pitches.

High           Pitches   Mix     | Low      Pitches   Mix
Fastball       133       0.56    |          284       0.64
Slider         76        0.32    |          83        0.19
Changeup       25        0.11    |          73        0.16
Curveball      4         0.02    |          7         0.02
Total          238       1.00    |          447       1.00

You can see from the table that when the pressure is mounting, Peavy relies less on his fastball and much more on his slider, throwing it 32% of the time in high pressure situations, compared with just 19% in low pressure situations. Nearly half of all sliders that Peavy threw in my sample have come in high pressure situations, while just one-third of all his fastballs came in high pressure situations. In every game that I examined, Peavy's ratio of fastballs to sliders was smaller in high pressure situations compared to low pressure situations, as he threw 3.4 fastballs for every slider in low pressure situations, but only 1.8 fastballs per slider in high pressure situations.

I was a little surprised that Peavy used his slider so much more in pressure situations. One reason for the difference could be that in low pressure situations, Peavy is more focused on getting quick outs and using more fastballs to do so. The fact that he used his slider more in pressure situations isn't surprising, but I was surprised by the magnitude of the shift. However, without someone similar to compare him to I wouldn't know if he really went to it more or if that was a pattern all pitchers shared. I used the other starting pitcher in the All-Star Game, Dan Haren, as my comparison. Haren relies on three pitches, a fastball, a slider and a split-fingered fastball, with a very occasional changeup and curveball mixed in. Here's a chart for Haren showing the same pressure situation splits.

High           Pitches   Mix     | Low      Pitches   Mix
Fastball       128       0.44    |          280       0.57
Slider         76        0.26    |          100       0.21
Splitter       82        0.28    |          92        0.19
Changeup       4         0.01    |          13        0.03
Curveball      0         0.00    |          2         0.00
Total          290       1.00    |          487       1.00

Whatever Peavy is doing with his slider in pressure situations, Haren is doing something very similar with his slider and splitter. Haren threw 28% splitters and 26% sliders in high pressure situations, compared with 19% and 21%, respectively, in low pressure situations. The ratio of Fastballs/Sliders and Fastballs/Splitters shows the same inverse relationship with pressure for Haren that it did with Peavy. One thing that really jumps out from these splits is the "out" pitch for each pitcher, not necessarily their best pitch, but the one they rely on to get outs. Looking at the basic chart, Peavy threw 61% fastballs, which makes it seem like that was his out pitch. However, he went hog-wild with his slider in pressure situations because that is his true out pitch. Haren relied on both his slider and splitter in pressure situations and used both of them for outs.

Both Peavy and Haren have different patterns that they follow when pitching in high and low pressure situations. Both pitchers use their off-speed pitches more in high pressure situations than in low pressure situations. This seems like it would be the norm in the Major Leagues, as pitchers would rely more on fastballs in low pressure situations, possibly to avoid walking batters and turning low pressure situations into high pressure one, and possibly to avoid showing their out pitches to batters. However, I can't know for certain whether Peavy or Haren throw a relatively high percentage of fastballs in low pressure situations because I don't have the Major League average for fastballs thrown in low pressure situations. That would need to be calculated before this type of analysis goes much further. With the MLB averages for the types of pitches thrown at different levels of pressure, game theory could be applied to the analysis, and statements like "Jake Peavy throws too many (or too few) fastballs in high pressure situations" would have real meaning.



Very interesting piece, nice job.

I would differ with your pitch characterization for Peavy, though. A change-up typically has similar movement to a fastball, only thrown slower (obviously). Your "5th pitch" meets this description and I believe that is a change-up.

The pitches you describe as slider and change-up are very similar and in fact, I would call them cutter and slider, respectively. The one I call the cutter is thrown slightly harder and has slightly less horizontal break than the slider, which is usually how we think of those pitches.

It's also interesting to note that if you consider cutter/slider together (slider/change in your tables), then Peavy throws the cutter/slider 43% of the time in high leverage situations and 35% of the time in low leverage pa's. There's still a difference, but it doesn't seem so great looked at this way.

Very cool.

One little thing you can try: I find leverage best split into three groups, and I typically use 0.70/1.40 as my threshholds. You'll end up with around a 50%/30%/20% split in terms of frequency. The 0.80-1.20 is really noise and clouds what you are really after.

If you aren't burned out on Felix Hernandez's pitch selection (God knows I am), you'll find another guy who does the same thing. With no one on, Felix just goes for the groundball. Get a man in scoring position, though, and you see him just pound the hitter with breaking balls in order to get the strikeout.

As The Book shows, there is an enormous run value difference between a K and a regular out, with a man on 3B and less than 2 outs.

In terms of pitching with men on base, I'd split it up into three categories:
- 3b less than 2 outs?
- if not, man on 1b?
- all others

You'd be best showing his pitch selection based on these three categories of men on base.

Thanks for the comments and suggestions so far and sorry in advance for the long post.


Actually classifying Peavy’s pitches was much tougher than I had thought it would be, (one problem is that the speeds and movements didn’t exactly line up with how I thought certain pitch types moved), but here’s my logic about how I did it. I looked at each start individually and classified each pitch type in each start. Looking at the start from 5/27, the only pitch that has a similar movement to his fastball is the red group, which has a speed somewhere around 88-90 MPH, which seems possible for someone throwing a fastball that is around 95-97 MPH. Sliders (and cutters) are slower than fastballs and have movement away from a RHH (when thrown by a RHP), so that’s what led me to label that pitch a slider. I thought that the green group was his changeup based primarily on the speed and frequency he threw it. The movement on it definitely surprised me, but the speed and frequency (compared to Inside Edge) seemed right.

I didn’t really explain why I removed the orange pitches in the article, but I went through and watched video of 10-15 or so of those pitches, and the announcers couldn’t agree with what they were. I realize announcers aren’t necessarily the greatest authority on pitch types, but when they called some of the orange pitches sliders, some fastballs and some changeups, I wasn’t too confident grouping them all in the same group. I suppose I should have done something like that for Peavy’s other pitches to see if the announcers were able to identify pitches, but I didn’t.

Even after going through each pitch, I’m still not totally certain about my classifications but something is changing depending on the splits, whether you call the pitch that changes a slider, a cutter or 2-seam fastball.


I like that and I’ll try it over the weekend and see what I get.


I’d love to do this with Felix if I get some time over the weekend, I’ll try to take a look if you want.

Have you looked at the release point data for the mystery pitches? Jake likes to drop down sidearm a couple of times per game; that my account for the 5th pitch.

Have you compared Peavy's pitches in May to his more recent outings? I saw a dropoff in velocity and movement, especially in the slider, and speculated he may have arm problems.


Regarding the drop in velocity and movement, MLB has started tracking the release point from different distances from home plate. Until June 4th, the release point was treated as 55 feet, but since then it has been varied between 40-50 feet. If you noticed the drop in velocity and movement via Gameday, thats a likely reason why.

In the article, when you say the slider moves toward RHB, is that a typo? As you say in your comments, a slider always moves away from a same side batter, by definition.

When I watch a game on TV I rarely do not know what a pitcher is throwing. I am always surprised at the number of mystery pitches on the gameday data. I wonder if it is more of a data problem than anything else. Can you look at video that corresponds to mystery pitchers?

Anyway, as I have said many time with regard to analyses of pitch selection, without knowing the norms for MLB pitchers on the whole and especially similar-type pitchers, these percentage analyses mean almost nothing. Of course Joe points that out and I am glad that he did.

There are only a few principal reasons to pitch differently in different leverage situations and I am not sure that looking at leverage is the best way to do it anyway.

You want to look at the win (not run) values of the walk, ball in play, batted ball out, and K. When the value of the K is a lot different than the batted ball out such as with a runner on third less than 2 out and a close game, obviously the pitcher wants to throw whatever gets him the most K's without worrying about a walk (unless perhaps the bases are loaded or to some extent with 0 out).

When leverage is low generally the pitcher wants to throw whatever are his best control pitches to minimize walks without worrying about hits. Also, I suppose he wants to limit his pitch count as much as possible even if it means letting up more runs.

Even in similar high leverage situations, the run values of the various outcomes can be quite different. Often a home run is what you want to avoid, such as a one run game in the 9th with no men on and sometimes it is just any hit, such as a runner on 2nd or 3rd with 2 outs in a tie or one run game.

When you want to avoid a home run, you pitch differently then just wanting to avoid a hit. And trying to avoid a hit or walk, such as with the bases loaded in a tie or one run game requires even a different pitching approach.

And of course, tracking location in addition to pitch type in different situations is important.


I did not know that; thanks for the info. I wish they'd hurry up and get this thing standardized and into all the parks.

At any rate, Peavy's slider does seem to have less break to it since May, at least that's how it seems watching on TV. Seems like he's had fewer missed swings on it as well.

this is all very fascinating.
however, peavy dosent have a fastball that "sits" in the high 90's. when a scout says a fastball "sits" in a certain range it means thats where his fastball is when the pitcher is throwing comfotably on most nights. peavy may touch 97 or 98 but on average he "sits" around 92 - 94 depending on what type of fastball he throws (cut, 2 seam, or 4 seam)

the only reason i bring it up is that i have nothing else to nit pick about in the article! its very interesting..although may be useless depending who u ask.

i meant to say i think his "5th" pitch is a cut fastball..he thew it once in the all star game to a left handed hitter at about 92 MPH..too fast to be a slider but still broke in on lefty...making it a cut fast ball...and it is common to see a varying MPH difference on a cut FB based on how it is gripped

You mentioned a "splitter" in the article. Peavy doesn't throw the splitter. He throws a straightish 4-seam FB, a sinking 2-seam FB (breaks from 12 to 5), a slider, a change (he should thrw more often), and a curve (he doesn't use as much as when he 1st came up)...

I just want to make a general point that it really doesn't matter what the pitcher or the coach thinks that a pitcher is throwing. All that matters is the result:
- speed
- spin
- trajectory

That combination will tell you all you need to know about the pitch. It's possible that one man's slider is another man's fastball in terms of how the pitcher thinks of it. But, all we care about is the perspective of the batter. A Jamie Moyer "fastball" could very well be a Billy Wagner "changeup".

I would standardize the nomenclature from the batter's perspective, not each individual pitcher's perspective.

That's an interesting point, tango. But the thing that makes a changeup effective is the speed difference between it and the fastball. Otherwise I think that is a valid point though. I made this page ( setting up unique parameters for each pitcher in excel to distinguish pitches and using arguments and formulas to doing something with those parameters.

It never occurred to me that the cutter and slider were two different pitches... I had just combined them as the slider. So this graph showing how Peavy's slider has progressed (or regressed) throughout the season is actually for the cutter and slider. SW% is what percentage of cutters/sliders are marked as swing strikes. Con% is the contact rate for those cutters/sliders swung at. SLG% is just on ct/sl hit into play. And I divided the break by 10 to fit into the graph; the gaps down and up are using different "release points". The X-axis would be pitches. Graph is here:
He is getting less swinging strikes, but not too much less: 2% decline in swinging strikes in the past month---month and a half. And it's been getting hit more and harder. I can't really say the break on the pitch has lessened though.

A slider generally has a more curvy trajectory (more horizontal + vertical break) compared to a cutter. Some elite hitters will see the break. For a RHP to a RHB, the pitch is generally thrown low and outside in an attempt to make the batter chase. Some pitchers may have 2 variations of a slider. One thrown hard with late break and one thrown softer with more loop. The one with more loop would be used to get a called strike thrown to the throwing arm side, regardless of which side the batter bats from.

The cutter is usually throw up in the zone, or at least that's where you want to throw it. The cutter is also generally used against an opposite side batter (RHP to LHP) thrown up and in. The pitcher is trying to jam the batter. Correctly thrown, the speed "should" be close to a fastball with late break, generally not much, but enough to make the batter not to make solid contact.

When the slider was first being used in MLB decades ago, it was suppose to have a very late break to it in order to fool the bater. Most of this generation's sliders will tend to be more loopy and "slurvy" because they don't properly develop it.

I agree with classifying based on speed, spin, and trajectory. The resulting pitch is more important the attempted pitch. Francisco Rodriguez throws what he calls a slider, but it has as much vertical movement has another man's curve. Some pitchers can't develop a changeup and may use a splitter or forkball as their "changeup".

How did you classify the pitches as FB, CB, SL, CH, etc? What I mean is did you hand-enter for the hundreds or use a program? If a program are you willing to share the SQL or formula you used?

For example, if you use straight speed ranges, Zambrano can throw an 89 slider/cutter and another pitcher that's a FB. Do you look at how much slower a pitch is from their top pitch? I am guessing here but please share whatever you are willing to.


I have a couple of points after reading some comments and talking with Rich. First, I goofed when I said Peavy's slider moved in towards a RHB. It should have been away from RHB (or towards a LHB), but that was a careless error on my part. However, I still believe that his changeup does move away from a RHB, which is different than most changeups. (The orange pitches are almost all from his start on 4/30. I'm in the process of watching that game on video and I'll post that later, but I still don't think they're changeups). Second, I was thinking about this when I was writing the article, but along the lines of what Tango and XV84 said, it doesn't matter what you call certain pitches. Peavy throws a curveball that is thrown around 79 MPH, breaks 6 inches down (compared to the spinless pitch) and 5 inches in on a LHB. Haren throws a splitter that is around 80 MPH with roughly a 2 inch drop and a 4 inch movement in on a LHB. I'm almost certain that if you looked, you could find a splitter that moves like Peavy's curveball and a curve that moves like Haren's splitter. There are certainly other differences between the curve and splitter (like their trajectory, rotation and maybe the time it takes them to reach home), but if two different types of pitches move the same, who cares what they're called. At some point during his dominant stretch with the Red Sox, Pedro was voted as having the best slider in the American League. When told of the award, he said something like 'that’s nice, but I don't throw a slider'.

BTW, there's no such thing as late break on a pitch, not unless they find out that thrown balls can have two axis of rotation, and I've never seen anybody claim that a pitcher can do that. Pitches (with the exception of the knuckleball) have the same amount of break to them throughout their entire flight path. Any perception that they do something different is simply a visual trick based on the perspective of the batter as he watches the flight of the ball toward him.

Uh, should read "two axes of rotation", duh.

BBAnalyst, if you were talking to me...

I'm not doing any profound; I'm not using any programming or things of that sort. I'm only using excel. If you're interested in what I'm doing in excel, email me at my yahoo address and I'll be more than willing to email you a sheet.

As usual excellent stuff by Joe. I agree with the comments regarding what a pitch is called…who cares. Pitchers are taught to throw the same pitches at different speeds to confuse batters. For example, a 90MPH FB thrown up and in “looks” like a 93 MPH FB to the hitter; the same FB thrown down and away at 87 “looks” like a 84 MPH FB to the hitter. On the gun there is only 3 MPH difference, but to the hitter it “looks” like 9MPH, which is enough to give a higher probability for a miss hit. Regarding late break, Nathanial is wrong; some pitches break later in their ball flight due to the physics of ball spin rates vs. ball velocity. To prove it to yourself go watch an accomplished pitcher up close.

It is interesting to see that Peavy (and others) tend to throw more breaking pitches in situations where the LI is higher. The pitching instructors I have been around teach pitchers to throw to bat contact (their contact) particularly in lower LI situations. In the most scenarios 70% will be outs and it is closer to 80%+ outs if the contact is at the pitchers desired contact point. Breaking pitches will induce more ground balls and will tend to get more strikeouts if the pitcher has been throwing more FB strikes in similar counts earlier in the game. However knowing he would be throwing more sliders in higher LI situations, I would be looking at more pitches if I was facing Peavy……… which would lead to more data for Joe to mine, which would lead to another article……which….. is why we all love this game….

I love these type of articles.

Im wondering if the data will ever been available as a full database with all the pitchers that pitched in this enhanced gameday settings.

some pitches break later in their ball flight due to the physics of ball spin rates vs. ball velocity.

Actually, you may be somewhat right there -- although you really didn't explain what you meant.

A pitched ball loses velocity on its way to the plate, while spin rate should remain constant. That would have the effect of increasing the break of the ball as it gets closer to the plate. By a little bit. It certainly wouldn't be much.

But that foward velocity is also what causes the force, called the Magnus force, that causes the baseball to break. The slower a ball is traveling through the air, the less this force is going to be in effect, lessening the amount of break the ball has.

These characteristics act in opposition, partially cancelling each other out. There would probably still be a slight increase in break as the ball gets near the plate, but far too small for the hitter to notice, especially when you realize that the hitter's eye can't even track the ball the last 6 feet to the plate.