## A Nibble Here, A Nibble There

We've already looked at the impact different factors have on whether a ball is called a strike or not. MGL suggested that I try and control for the fact that certain pitchers are much more likely to hover around the edge of the plate rather than down the middle or "just a bit outside".

Generally, any time MGL makes a suggestion, it's a good idea to at least consider it. So I went ahead and re-ran all the same splits except the one based on how a pitcher started a game, using the same approach as in my previous articles. The change is that I only looked at pitches within two ball widths (just under 6 inches) of the edge of the strike zone (either inside or outside the zone).

I also tweaked my run value of a "mistake" thanks to a comment from Iblemetrician that pointed out that missed pitches are probably more likely to occur at some counts rather than others. The value I'm using for these results is .133 runs per mistake, which is substantially lower than the original value of .161.

There's also going to be some level of trickery here. I'm going to continue to display all numbers in terms of runs/150 pitches just so we can get a better idea of how the old values compare to the new values. But since we're only looking at close called pitches in the second case, we get fewer per game - only about 70 compared to 150. So even if the runs per 150 pitches look a lot higher in the new tables, the actual effect on the game might be less. For a quick conversion to runs per game for the close called pitches, divide by 2.

I'm going to present the numbers from last time again (using the new run value) so we can see how they compare to the close pitches. This should allow us to get a better handle on what the bigger determining factor is - the number of pitches on the edges, or how those pitches are called. I've left out the graphs this time because they don't really show any tremendous differences.

A couple of labeling notes to keep in mind: CP = Called Pitches, CCP = Close Called Pitches

And finally, before we get started, the disclaimer. These splits are not necessarily indicative of skill. They measure less than one full season and include many other factors that should be corrected for. As time passes, we should be able to complete more technically rigorous analysis (that's the royal we, as in someone else who knows more about statistics) that may begin to clarify what percentage is skill and what percentage is unexplained/random variation. Until that time, I strongly recommend not using this information for anything more than entertainment purposes.

## Game Specific Factors

### Inning

Called Pitches By Inning
Inning CP % of Total CP Runs / 150 Pitches
1 21281 12.8 0.09
2 19165 11.5 0.01
3 19076 11.5 -0.04
4 18093 10.9 0.03
5 18209 10.9 -0.02
6 18028 10.8 -0.07
7 18482 11.1 0.01
8 18482 11.1 -0.03
9 13029 7.8 0.05
10+ 2588 1.6 -0.15
Close Called Pitches By Inning
Inning CCP % of Total CCP Runs / 150 Pitches
1 11385 13.1 0.12
2 10395 11.9 -0.04
3 10019 11.5 -0.12
4 9345 10.7 0.02
5 9405 10.8 -0.04
6 9214 10.6 -0.10
7 9464 10.9 0.11
8 9629 11.1 -0.08
9 6783 7.8 0.22
10+ 1352 1.6 -0.36

Wow. The obvious thing that jumps out here is how well pitchers do on close pitches in the ninth inning. Following up from my last article, I feel more confident suggesting that the quality of the pitcher plays a role in which way the calls go. Closers appear to get the benefit of the doubt, while the extras appear to be left to the back of the bullpen. I'd still like to think there's some sort of umpire fatigue that explains the extra innings too. It just seems too human an explanation to ignore.

### Home or Visitor

Called Pitches By Pitching Team
Pitching Team CP % of Total CP Runs / 150 Pitches
Home 84524 50.8 0.05
Visitor 81909 49.2 -0.05
Close Called Pitches By Pitching Team
Pitching Team CCP % of Total CCP Runs / 150 Pitches
Home 84524 50.9 0.08
Visitor 81909 49.1 -0.09

I changed around the labels this time to try and make things more clear. It's now organized according to pitching team - so the positive number for the Home team is actually a positive benefit for the pitchers.

Beyond the change in labels, there's really no difference in looking at the edges versus all pitches - still a slight advantage to the home team.

## Pitcher Factors

### Age

Called Pitches By Age
Age CP % of Total CP Runs / 150 Pitches
20 2790 1.7 0.10
21 2944 1.8 0.00
22 4507 2.7 -0.13
23 11582 7.0 -0.23
24 13041 7.8 -0.14
25 15982 9.6 -0.15
26 15387 9.2 0.04
27 17369 10.4 -0.16
28 11809 7.1 -0.10
29 15636 9.4 0.23
30 13211 7.9 -0.01
31 7844 4.7 0.17
32 5177 3.1 0.12
33 8705 5.2 0.01
34 2392 1.4 .16
35 3190 1.9 0.14
36 3187 1.9 0.09
37 1851 1.1 0.60
38 903 0.5 0.49
39 2645 1.6 0.31
40 2184 1.3 0.31
41 1603 1.0 0.33
42 276 0.1 -0.84
43 1498 0.9 0.05
45 720 0.4 0.59
Close Called Pitches By Age
Age CCP % of Total CCP Runs / 150 Pitches
20 1488 1.7 0.18
21 1541 1.8 0.02
22 2340 2.7 -0.25
23 6060 7.0 -0.46
24 6675 7.7 -0.23
25 8367 9.6 -0.30
26 7986 9.2 0.05
27 9230 10.6 -0.26
28 6140 7.1 -0.12
29 8064 9.3 0.47
30 6899 7.9 -0.03
31 4143 4.8 0.35
32 2676 3.1 0.16
33 4571 5.3 0.07
34 1256 1.4 0.31
35 1627 1.9 0.32
36 1672 1.9 0.10
37 1006 1.2 1.04
38 448 0.5 0.89
39 1345 1.5 0.51
40 1222 1.4 0.33
41 928 1.1 0.26
42 134 0.2 -1.35
43 805 0.9 0.06
45 368 0.4 1.13

The most surprising thing here is that the proportions for each age stayed pretty close from all called pitches to the pitches on the edge. I thought (and it was suggested by more than one person) that older pitchers would be be more likely to nibble and therefore we'd see a higher proportion of close pitches going to the elders. That's clearly not the case, as you can see even more clearly below. This means that the difference according to age is mostly composed of selection bias and umpires actually giving older pitchers the benefit of the doubt.

Called Pitches by Age Groups
Age CP % of Total CP Runs / 150 Pitches
Under 25 50846 30.6 -0.12
26-35 97530 58.6 0.03
Over 35 18057 10.8 0.25
Close Called Pitches by Age Groups
Age CCP % of Total CCP Runs / 150 Pitches
Under 25 26471 30.4 -0.25
26-35 50965 58.6 0.06
Over 35 9555 11.0 0.37

### Experience

Called Pitches by Experience
Experience CP % of Total CP Runs / 150 Pitches
0 17814 10.7 -0.11
1 20275 12.2 -0.16
2 21048 12.6 -0.07
3 16597 10.0 -0.16
4 14579 8.8 -0.05
5 11218 6.7 0.09
6 10098 6.1 -0.03
7 9716 5.8 0.12
8 13236 8.0 0.04
9 6638 4.0 0.23
10 6063 3.6 0.29
11 1868 1.1 0.24
12 3914 2.4 0.33
13 499 0.3 -0.41
14 2722 1.6 0.30
15 3541 2.1 -0.11
16 863 0.5 0.62
18 929 0.6 0.50
19 1494 0.9 0.56
20 1625 1.0 0.17
21 1522 0.9 0.26
23 139 0.1 0.53
Close Called Pitches by Experience
Experience CCP % of Total CCP Runs / 150 Pitches
0 9273 10.7 -0.22
1 10584 12.2 -0.25
2 10874 12.5 -0.08
3 8724 10.0 -0.15
4 7594 8.7 0.22
5 5909 6.8 -0.17
6 5310 6.1 0.00
7 4967 5.7 0.08
8 6846 7.9 0.07
9 3511 4.0 0.38
10 3277 3.8 0.50
11 958 1.1 0.78
12 2041 2.3 0.26
13 240 0.3 0.24
14 1496 1.7 0.41
15 1889 2.1 -0.00
16 454 0.5 1.03
18 443 0.5 0.21
19 769 1.0 0.92
20 863 1.0 -.81
21 878 1.0 -.33
23 69 0.1 0.94

Called Pitches by Experience Groups
Experience CP % of Total CP Runs / 150 Pitches
Under 2 59137 35.5 -0.11
3-7 62243 37.4 -0.03
Over 8 45053 27.1 0.18
Close Called Pitches by Experience Groups
Experience CCP % of Total CCP Runs / 150 Pitches
Under 2 30731 35.3 -0.20
3-7 32526 37.4 -0.04
Over 8 23734 27.3 0.32

Looking at experience shows pretty much the same thing as age - which is what I'd expect since they're so closely correlated.

### Handedness

Called Pitches by Hand
Hand CP % of Total CP Runs / 150 Pitches
Left 44213 26.6 -0.07
Right 122220 73.4 0.03
Close Called Pitches by Hand
Hand CCP % of Total CCP Runs / 150 Pitches
Left 23174 26.6 -0.15
Right 63817 73.4 0.05

There's nothing too interesting in this comparison. Righties still have a slight advantage over lefties.

### Runs Allowed

Called Pitches by Runs Allowed
RA/9 CP % of Total CP Runs / 150 Pitches
Less Than 4.00 30491 20.5 -0.01
4.00-6.00 97973 66.0 0.05
More Than 6.00 20086 13.5 -0.20
Close Called Pitches by Runs Allowed
RA/9 CCP % of Total CCP Runs / 150 Pitches
Less Than 4.00 16069 20.7 -0.05
4.00-6.00 51199 66.0 0.09
More Than 6.00 10416 13.5 -0.37

Again, nothing to see here. (I suppose I'm expected to say "Pass.")

### Walk Rate

Called Pitches by Walk Rate
BB/9 CP % of Total CP Runs / 150 Pitches
Less Than 2.50 21241 14.3 0.15
2.50-4.50 102769 69.1 0.01
More Than 4.50 24540 16.5 -0.18
Close Called Pitches by Walk Rate
BB/9 CCP % of Total CCP Runs / 150 Pitches
Less Than 2.50 11524 14.9 0.25
2.50-4.50 53698 69.1 0.02
More Than 4.50 12462 16.0 -0.30

There is a slight variation here in the percentage of total pitches for each category. Sure, .6% isn't very big, and could easily have no identifiable cause, but it does look like pitchers with good control have more called pitches near the edges. That's not very surprising of course, since they're likely going to have fewer called pitches well outside the strike zone (those are largely balls), which means more will be in or around the strike zone.

## Summary

Here we are again - the what does this all mean moment. As I disclaimed up top, it's too soon to tell. Before we go any further, let's bring the summary charts from the other article, where we look at the largest possible spread in ERA for a given split.

ERA Effect for All Called Pitches
Breakdown Good Bad ERA Effect
Inning First Extras .03
Pitching Team Visitor Home .01
Age (Buckets) Over 35 Under 25 .04
Experience (Buckets) Under 2 Over 8 .03
Handedness Righties Lefties .01
Runs Allowed 4.00-6.00 More Than 6.00 .03
Walk Rate Less Than 2.5 More Than 4.5 .04
ERA Effect for Close Called Pitches
Breakdown Good Bad ERA Effect
Inning Ninth Extras .03
Pitching Team Visitor Home .01
Age (Buckets) Over 35 Under 25 .03
Experience (Buckets) Under 2 Over 8 .03
Handedness Righties Lefties .01
Runs Allowed 4.00-6.00 More Than 6.00 .02
Walk Rate Less Than 2.5 More Than 4.5 .03

So even though the spread between best and worse is generally a lot bigger for the close pitches, the fact that they only happen about half as often drives the actual effect to be the same or less than for all called pitches. That's not to say that half the effect is from close called pitches and the other half from no-doubters. It looks like most of the mistakes, and most of the variation, occurs on close called pitches. However, there doesn't appear to be a whole lot of accuracy gained on the runs/game level by breaking out only the pitches on the edges.

That said, we did learn a few things. Surprisingly, there appears to be very little difference between age groups in the amount of called pitches that are near the edges. That seems to go against the conventional wisdom of older pitches starting to place their pitches more as they lose a little off their fastballs. I wonder how many pitchers really do make that transition successfully, and how many keep following the same strategy and either succeed (and not change) or fail (and retire). These numbers suggest not too many really do change their approach too much.

To wrap up, again I caution you against reading too much into these results. There's way too many unknowns and, even worse, known issues with the data and the criteria used to determine the splits to make them that useful. They can be used to start discussion and further research, but I definitely wouldn't try to work them into projections any time soon.

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