Designated HitterDecember 07, 2006
Expanding the Strike Zone
By David Appelman

About a year ago, I wrote an article entitled Pitchers, Pitch by Pitch. Using pitch location data from Baseball Info Solutions, I looked at how often individual pitchers get batters to chase pitches outside the strike zone, or in other words, swing at pitches they shouldn't be swinging at. I called this stat Outside Swing Percentage or OSwing, for short.

To recap: OSwing correlated with a pitcher's strikeout-to-walk ratio and just for fun, let's look at the starting pitchers and relievers who had the highest OSwing the past two seasons.

Name                     2005    Name                   2006
Brad Radke             31.76%    John Smoltz          33.00%
Johan Santana          30.21%    C.C. Sabathia        31.47%
Curt Schilling         29.60%    Jeremy Bonderman     31.01%
Felix Hernandez        28.43%    Roger Clemens        30.88%
John Smoltz            27.53%    Curt Schilling       30.76%
Odalis Perez           27.47%    Johan Santana        30.72%
Jon Lieber             26.44%    Jake Peavy           30.61%
Rich Harden            26.00%    Roy Halladay         29.55%
Andy Pettite           25.97%    Odalis Perez         29.16%
Paul Wilson            25.33%    Aaron Harang         28.91%
Name                     2005    Name                   2006
Brad Lidge             32.41%    Cla Meredith         37.88%
Rudy Seanez            30.93%    Patrick Neshek       35.92%
Mike Wuertz            28.67%    Mariano Rivera       34.13%
Derrick Turnbow        28.40%    Mike Wuertz          32.57%
Jonathan Papelbon      28.27%    J.J. Putz            32.18%
Julio Santana          28.01%    Brian Sikorski       32.00%
Bobby Jenks            27.68%    Francisco Rodriguez  31.65%
Kyle Snyder            27.06%    Dennys Reyes         31.56%
Tyler Walker           26.71%    Scott Proctor        31.54%
Eddie Guardado         26.69%    Ramon Ramirez        31.31%

All in all, some fairly prestigious lists, especially the 2006 list of starting pitchers, but OSwing is hardly a "magic bullet stat" since there are some players on these lists I'm sure you're scratching your head at. Let's take a step back for a moment and think about the relationship between batters and pitchers.

Ideally, a pitcher is going to try and get ahead in the count and when this happens the pitcher has effectively "expanded the strike zone" since the batter is now on the defensive and will be more prone to chase pitches outside the strike zone. Conversely, when a pitcher is behind in the count, a batter will be less prone to chasing bad pitches. Looking at OSwing by count this becomes fairly evident.

Count         OSwing         ZRatio
0-0           11.33%           1.15
0-1           22.54%           0.83
0-2           31.57%           0.51
1-0           18.61%           1.31
1-1           26.78%           1.05
1-2           37.37%           0.70
2-0           16.38%           1.61
2-1           28.58%           1.41
2-2           41.40%           0.98
3-0            2.69%           1.73
3-1           23.37%           1.67
3-2           44.86%           1.57

Furthermore, if you look at the ratio of balls thrown in the strike zone to those outside the strike zone (ZRatio), you can see that when a pitcher is ahead in the count, he's much less likely to pitch in the strike zone. So, is how often a pitcher gets a batter to chase a ball outside the strike zone merely a matter of his skill at managing the count?

Not exactly. While the two are hardly mutually exclusive, some pitchers do seem to be able to make batters chase pitches outside the strike zone more than others in the various counts. Here are the 15 starting pitchers who get ahead in the count the most and their OSwing above (or below) the MLB average when ahead in the count.

Starter              OSwing(Above Average)         Ahead%
Johan Santana                      22.89%          33.91%
Curt Schilling                     19.34%          33.74%
John Smoltz                        27.29%          33.55%
Mike Mussina                       -4.35%          33.27%
Roy Oswalt                          6.43%          33.21%
Elizardo Ramirez                   -1.56%          32.84%
C.C. Sabathia                      37.21%          32.81%
Brad Radke                          4.99%          32.35%
Paul Byrd                           3.93%          31.97%
Jon Lieber                          1.01%          31.68%
Francisco Liriano                  20.35%          31.37%
Randy Johnson                      19.13%          30.73%
Pedro Martinez                      3.40%          30.72%
John Lackey                        17.62%          30.64%
Cliff Lee                           1.93%          30.55%

As you can see, many of the top pitchers in baseball get ahead in the count, but they don't always have the same success getting batters to swing at their pitches outside the strike zone. Let's have a look at the relievers:

Starter              OSwing(Above Average)         Ahead%
Patrick Neshek                     30.22%          39.82%
Rafael Betancourt                  -1.81%          39.64%
Chad Bradford                      -3.44%          36.69%
Jose Valverde                     -12.64%          36.26%
Mike Timlin                         9.34%          35.78%
Trever Miller                      14.74%          34.99%
J.J. Putz                          18.50%          34.93%
B.J. Ryan                          10.92%          34.92%
Todd Jones                          8.87%          34.75%
Justin Duchscherer                  5.01%          34.62%
Rafael Soriano                     25.02%          34.49%
Mariano Rivera                     30.22%          33.73%
Matt Capps                          4.88%          33.60%
Jonathan Papelbon                  22.20%          32.78%
Cla Meredith                       71.75%          32.78%

Once again, pretty much the same deal with the relievers. It's worth noting that Cla Meredith's 71.75% above average OSwing was by far the highest in baseball when ahead in the count. Batters swung at just over half the pitches he threw out of the strike zone.

Just looking at these two lists, I'd venture to say that the pitchers who more often than not get ahead in the count, and those who were also able to get batters to chase pitches more than the MLB average would probably be the most dominant pitchers in baseball. Let's look at one final list where the pitchers are at least 15% above the MLB average in OSwing and percent ahead in the count.

Name            OSwing(Above AVG) Ahead%(Above AVG)  ERA      K9    BB9
Patrick Neshek            30.22%          46.24%    2.18   12.89   1.45
J.J. Putz                 18.50%          28.26%    2.29   11.94   1.49
Rafael Soriano            25.02%          26.65%    2.25    9.75   3.15
Johan Santana             22.89%          24.54%    2.77    9.43   1.81
Curt Schilling            19.34%          23.92%    3.97    8.07   1.23
Mariano Rivera            30.22%          23.88%    1.80    6.60   1.32
John Smoltz               27.29%          23.22%    3.49    8.18   2.13
C.C. Sabathia             37.21%          20.48%    3.22    8.03   2.05
Jonathan Papelbon         22.20%          20.38%    0.92    9.87   1.71
Cla Meredith              71.75%          20.37%    1.06    6.57   1.06
Matt Thornton             15.10%          18.31%    3.33    8.16   3.50
Scott Proctor             25.63%          17.25%    3.51    7.82   2.90
Bill Bray                 29.43%          17.08%    4.08    6.92   3.19
Brian Sikorski            27.47%          16.14%    5.02   10.05   1.85
Alan Embree               36.32%          15.81%    3.26    9.11   2.57
Joe Nathan                20.58%          15.48%    1.58   12.51   2.10
Francisco Liriano         20.35%          15.20%    2.15   10.71   2.38
Brandon League            23.21%          15.09%    2.53    6.11   1.89

A pitcher's ability to expand the strike zone is something that is widely talked about, but rarely quantified. What I find most fascinating about all this is that by using location data, it should be possible to see exactly how far and where the strike zone expands/contracts for individual pitchers and batters depending on the count. It sounds like the type of information that could really make a difference in statistical scouting reports. But that's another project for another day.

David Appelman is the creator of You can contact him via e-mail.


Very cool.

Quick question: only two of the starters from the '05 top 10 made it to the '06 top 10. Do we know how well this correlates year-to-year?

Just looking at 2005 & 2006, it has an r^2 of about .27 with pitchers who threw at least 500 pitches in both seasons.

I was going to make the exact same comment as Nolan, so I'll ask the follow up instead.

Quick question: are we disappointed by the lower r^2 value?

ps. Very Cool!

I don't have multiple year r^2's for walk rate and strikeout rate on hand... but just looking at 2005-2006 with the same group of pitchers:

K/9 - .5
Unintentional BB/9 - .3
ERA - .09

It's probably worth mentioning that I found the average 2006 OSwing about 3% higher than 2005. I don't know if this is due to improvements in pitch location charting or just random year to year variance. I'll be sure to take another look at this next year. These pitch location studies are hardly "set in stone" and very much an ongoing project.

Brad Lidge led relievers in 05. Obviously he had his problems in 06. What was Lidge's percentage in 06? I'm just curious to see how far it dropped between 05 and 06. A key to Lidge's strike outs is the swing and miss at his slider in the dirt. People frequently stated that batters quit swinging at Lidge's slider in 06, thereby increasing his walks and causing him to have to throw fastballs in bad counts.

Lidge saw a slight decline from 2005 - 2006 in actual OSwing, but it was only 2%. But, considering the baselines are different from 05 and 06, if you do % over league average, he went from about 59% better than the average pitcher to 26% better.

It'd be interesting to see if he was throwing his fastball more and in what counts. His strikeouts are still pretty off the charts and his walk rate isn't that bad. It doesn't look like OSwing really sheds any new light on his troubles.