I don’t believe pitchers should go past 100 pitches. That might seem like the view of a baseball luddite, but it’s quite simple. Throwing 100 pitches means six innings. Surviving six innings equates to 27 batters. Facing 27 batters impends the fourth time through the order. And that spells doom.
As a rule of thumb—not without exceptions—a decent reliever coming out of the bullpen will be better than all but the best of starting pitchers facing the fourth time through the order. Batters make adjustments, and there’s little a pitcher can do.
So I don’t think fatigue has much to do with the 100-pitch rule. However, I do think the subject of pitcher stamina is interesting in itself. Behold:
No pitcher fades as severely as Jonathan Sanchez.
Here’s how I arrived at that conclusion. First, I tried to correct the velocity using a similar method as outlined by Mike Fast yesterday, but only using the fastest 25% of pitches by every pitcher. Then, I took the 25% fastest pitches for every pitcher at every pitch count. This would hopefully provide an unbiased measure of fastballs as the game went on. I found the difference in velocity between each of those pitches and the average pitch velocity in each game.
Here’s how it looks on a league-wide basis:
There is a phenomenon with regard to the first pitch of a ballgame. Pitchers throw fastballs at an exceedingly high rate on the first pitch, and batters refuse to swing. I’ve noticed that some smart players (such as Derek Jeter) will take advantage of such predictability. After that, pitchers will work their hardest against the most difficult batters in the batting order from pitches 10-20, and then fade a bit as the game goes on, until they hit the fourth time through, when they really gear up.
Few are able to enter another gear like Justin Verlander:
I ran a regression of velocity on pitch count, controlling for the pitcher, and found that the following starters, over the course of 100 pitchers, will either gain a half a mile per hour in velocity or lose at least one mph.
One other notes of interest: there were reports early last season of a spike in Mike Minor’s velocity. Minor was reportedly a finesse pitcher coming out of Vanderbilt, but he debuted in the Majors throwing in the low 90s. By September, Minor complained of fatigue. As it turns out, Minor also fatigues rapidly within games:
Pitch counts aren't the only reason for fatigue; time is another potential culprit. To test for time's effect on velocity, I controlled for pitch count. At 10-15 pitches, a pitcher has generally been on the mound for about five minutes. My data showed that pitchers threw over a tenth of a mile per hour faster when they had been out there under five minutes than when they'd passed the five minute mark. In general, at the same pitch count, the more time has elapsed since a pitcher’s first delivery, the softer he throws.
Next week, I hope to look at how time between innings may impact velocity. The thing to keep in mind with all of this is that every pitcher reacts in his own way to these stresses. The data would indicate that most all pitchers should be pulled before they reach the fourth time through the order, and that there's no way of telling how most any pitcher is throwing given his pitch count without an awareness of his individual history. The 100-pitch mark isn't when pitchers tire—different athletes tire at their own rates throughout the entire course of competition. The crucial factor here isn’t fatigue, but times through the order. Limiting pitchers to 100 pitches seems to be the right rule, but for the wrong reasons.