When Do Pitchers Try Harder?

Pitch counts have become an integral part of the game of baseball, so much so that it’s impossible to find a TV telecast that doesn’t display the pitch count side-by-side with the score and the inning. Yet pitch counts continue to be maybe the most annoyingly simple and arbitrary metric used to craft crucial in-game strategy. 99 mph fastball down the middle: +1 pitch. 76 mph curveball in the dirt: +1 pitch. Intentional ball: +1 pitch. Dirty ball tossed to the umpire: +0 pitches. Pitchout +1 pitch. Warmup pitches: +0 pitches. My goal here is not to fix this problem — just explore some interesting data that I believe should eventually be used to bring pitch count into the modern era.

Right now, I’m just going to look at 4-seam fastballs and how hard they’re thrown. All data comes from the 2016 regular season. Thank you Baseball Savant. The question I set out to answer is simple: When a pitcher needs to make a pitch, does he try harder? Common sense says yes, of course this is what happens. Relievers throw harder than starters in general because they don’t have to worry about throwing more quality pitches in later innings. But the data shows that pitchers change their effort levels within innings as well, especially when they have two strikes and/or runners in scoring position. Eventually, we should be able to use this knowledge to craft a better pitch count that takes this extra effort into account.

I downloaded every 4-seam fastball thrown in 2016 in each of 72 categories. The categories were broken down by count, number of outs and runners on base. So 0-0, no outs, nobody on is one category, as is 3-2, two outs with runners in scoring position. It turns out that the number of balls is mostly a non-factor, so I simplified the breakdown by ignoring balls and instead using no strikes, one strike and two strikes. The average release velocities for each of these situations can be seen in the table below.

	0 outs	0 outs RISP	1 out	1 out RISP	2 outs	2 outs RISP
0 strikes	92.28	93.00	92.86	93.13	93.12	93.37
1 strike	92.76	93.18	93.17	93.31	93.30	93.50
2 strikes	93.49	93.63	93.67	93.87	93.79	93.97

At its most basic level, you can see that the highest average velocity is for pitches thrown with two outs, two strikes, and runners in scoring position while the lowest is for no outs, no strikes and the bases empty. We can see that for zero, one, and two outs, pitchers throw harder with runners in scoring position than with the bases empty (though the difference is larger for no strikes than it is for one and two strikes) and that regardless of the situation, pitchers throw harder with two strikes than they do with zero or one strike.

These are small differences, though, most less than a single mile per hour. We can use a difference of means t-test to determine whether these differences are, in fact, signal, or if they can be explained by random fluctuations. Since this isn’t a high school math assignment, I’m going to skip explaining my work, but you can be assured that most of these differences — due to the relatively low variance and high sample size — are, in fact, significant.

You can peruse the data table above (or the full one included below) at your own leisure, but there are a few things that I think are important to point out. First, there is one alternate explanation besides differences in effort for this effect that I can think of: Maybe pitchers with better (read: faster) fastballs are more likely to throw fastballs in these situations than other pitchers. Certainly you’d expect more 3-2 fastballs from Aroldis Chapman than from Jered Weaver and this is, in fact, the case. Weighting by the number of pitches thrown, pitchers who threw two-strike, two-out fastballs with RISP in 2016 had an average fastball velocity 0.3 mph harder than pitchers who threw two-strike, two-out fastballs with no runners on. This effect, too, is statistically significant, but it is much smaller than the total difference in velocity, so these effects are likely working together to create the total velocity difference shown in the tables above.

Going back to the original issue, another interesting fact is that pitchers seem to put more effort into two-strike pitches than they do into pitches with runners in scoring position. We see for zero, one, and two outs that two-strike pitches with no runners on have a higher average velocity than no-strike pitches with RISP. It would be interesting to see if this trend holds true for older seasons when less emphasis was put on the strikeout.

The next steps will be to see if these trends hold true for offspeed pitches as well. The path to answers will be less clear. Will we be able to distinguish higher-effort curveballs from their velocities or from their spin rates (there is no difference in fastball spin rate)? What about changeups? And then how will we compare effort levels across pitches? There’s a lot of work still to be done, but I think these results provide an interesting jumping-off point. Feel free to add your own observations in the comment section.

	0 outs	0 outs RISP	1 out	1 out RISP	2 outs	2 outs RISP
0-0	92.22	92.94	92.89	93.15	93.18	93.48
0-1	92.64	93.25	93.23	93.36	93.35	93.52
0-2	93.27	93.49	93.68	93.84	93.77	93.91
1-0	92.44	93.06	92.90	93.19	93.12	93.25
1-1	92.82	93.13	93.16	93.32	93.32	93.50
1-2	93.53	93.70	93.68	93.91	93.83	94.01
2-0	92.45	93.32	92.78	93.04	92.96	93.30
2-1	92.90	93.16	93.17	93.22	93.26	93.56
2-2	93.63	93.73	93.69	93.93	93.80	94.03
3-0	92.06	92.71	92.41	92.81	92.61	92.89
3-1	92.73	93.13	92.95	93.29	93.16	93.33
3-2	93.47	93.54	93.65	93.76	93.73	93.88