Last week, I wrote about different age groups and differences in the way they pitch. I received a couple of comments about certain ways to further create groups and try to isolate the differences I saw, and in doing that, I came up with some interesting new material for this week's article.

In last week's article, I had two groups: old and young pitchers. This week, I split my age groups into two groups based on the speed of their fastball. The "young-slow" group was young pitchers who had an average fastball speed of 90.5 MPH or lower, and the "young-fast" group was comprised of the rest of the pitchers originally in the young group. I did the same thing with my group of old pitchers, and ended up with 4 different groups, which are summarized in the table below, along with the groups from last week for perspective.

Group        N    FB Spd  FB%    CH%    CB%    CT%    SL%
Young-slow   22   88.1    0.53   0.13   0.12   0.04   0.17
Young-fast   59   93.1    0.59   0.13   0.10   0.04   0.14
Old-slow     45   87.8    0.53   0.19   0.09   0.05   0.14
Old-fast     26   92.8    0.48   0.14   0.07   0.09   0.23
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Old-all      71   89.9    0.50   0.17   0.08   0.07   0.18
Young-all    81   92.1    0.58   0.13   0.10   0.04   0.15

There are a couple of really interesting bits in the table, the first being the FB% of the old-fast group being lower than the FB% of the old-slow group. One reason for this apparent inconsistency is that the fast group is made up of players who have retained a very effective breaking ball even as they aged (mostly sliders and cutters), which they rely heavily on.

Here's a chart that highlights some important features about the sliders in each group. The old-fast group actually has the fastest slider, but the important parts of this table are the last two columns. One quick way for judging the "nastiness" or effectiveness of a pitch is to see how often a pitcher is able to get a swing and miss from it. The final two columns show the swing and miss percentage for sliders and fastballs in each group. These break down pretty nicely along speed lines, with the faster groups getting more swings and misses than the slower ones. What is a little bit surprising, especially in light of the frequency table, is how similar the speed groups are to each other for sliders and fastballs. The pitches move slightly differently for the two fast groups (and slow ones), but there isn't a whole lot of difference in how often batters swing and miss it. The similarity is surprising because of how often the two fast groups throw their fastball with the hard-throwing old pitchers throwing the fewest amount of fastballs with their younger counterparts throwing the most. Some of that difference is explained by difficulty controlling the slider vs. fastball, but it seems like hard-throwing young pitchers are being over-reliant on fastballs as a group. The flip side to this is that hard-throwing old pitchers could be throwing fastballs at closer to the optimal rate and preferentially throwing them when needed.

Group        SL Spd   pfx_x    pfx_z    SL-SandM%   FB-SandM%   FB-SLGBIP
Young-slow   82.3     4.74     3.44     0.11        0.05        0.552
Young-fast   85.1     2.98     3.43     0.14        0.07        0.592
Old-slow     81.1     2.66     4.02     0.10        0.05        0.580
Old-fast     86.2     3.00     4.13     0.15        0.07        0.509

This possibility of old hard-throwers leveraging their fastballs better than younger ones also shows up in the results as well. The young-fast group had the highest SLGBIP on their fastballs while the old-fast group had the lowest and while this isn't the strongest evidence for the old pitchers picking their spots with their fastballs, but it's a start. Looking at fastball selection either by count or hitter quality is the next step here.

I mentioned last week how the younger population was made up of both players who would eventually join the old group and players who wouldn't. This is a "duh" statement, but I think the pitchers who will survive and eventually make it into the old group would tend to come out of the young-fast group. That group can afford to lose some velocity on their pitches and still be effective, but the young-slow group is already on the edge of being very hittable and has nowhere to go if they suffer a drop in velocity. Obviously the attrition doesn't just come from the slow group, but everything else being equal, I would rather bet on a hard thrower having a longer career than a slow thrower. Looking at the list of names in each group reinforces this idea too. The slow group has only 22 names on it, but most of them wouldn't be considered top-prospects. The highlights include Dallas Braden, Kyle Kendrick, Zach Duke, and Carlos Villanueva. The fast list is full of either prospects or young guys who have already established themselves, including Justin Verlander, Matt Cain, Tim Lincecum, Felix Hernandez, and Scott Kazmir.