Pitch Counts and Pitchf/x
I remember Randy Johnson throwing 99 to finish a complete game. Back in their day, Nolan Ryan and Bob Feller probably did that on a regular basis (if you were to ask them). There's a lengthy list of early 20th century pitchers who pitched complete games in both ends of a doubleheader. So what's the driving force behind the pitch count craze? Are we going soft?
I don't think there's some grand scheme to baby pitchers. I do think that pitchers nowadays exert exponentially more effort on each pitch than pitchers of yesteryear, but our contemporaries could still probably hold up past the hundred pitch mark. The main reason pitchers get pulled before they reach their limit is because there's little incentive not to pull them. Take a look at baseball reference's splits. Pitchers allow a .726 OPS the first time through the order, then the OPS jumps 40 points the next time through and another 40 points after that. So managers make the correct decision to insert a reliever who has the advantage of facing batters for the first time. With eight-man bullpens, there's no reason not to go to a reliever early. So the question becomes not if, in the current environment, we should continue to adhere to pitch counts, but why? Does the pitcher lose effectiveness, or does the batter adjust to even the fastest of fastballs having already seen in in his three previous plate appearances?
With pitchf/x data, you can tease out the pitcher's part in the pitcher/batter matchup. A pitcher really controls five things:
-Where the ball is released
-Where the ball lands
-How hard the ball is thrown
-How much the ball spins
-What direction the ball spins
Here, I will concern myself with the final three components, which I believe define what we call a pitcher's "stuff." For example, the average fastball from a right-handed pitcher (92 MPH, nine inches of rise, seven inches of run) is worth about half a run below average per 100 pitches. I will call that its StuffRV. The following graph demonstrates the average StuffRV (per 100) and a smoothed out actual run value (per 100).
There's a lot going on here.
-Our main concern is with a pitcher's endurance with regards to his stuff. The takeaway from this graph, then, is that from a pitcher's 10th pitch to his 60th pitch, his stuff will deteriorate by about a 10th of a run per 100 pitches.
-My methodology grades out fastballs as inferior to breaking balls. You can tell by looking at the very first mark on the graph. A pitcher's first pitch of the day is a fastball about 80% of the time, while in total, pitchers throw fastballs 60% of the time. On an 0-0 count otherwise, pitchers throw fastballs just under three quarters of the time. Same as on pitches two through ten: 70-75%. For some reason, pitchers like to start their outings off with a fastball.
-A pitcher's success is, of course, largely dependent on the batter, and you can see when each lineup spot tends to hit by following the true run value curve. Pitchers face the eighth and ninth batters in the order generally during their 25th to 35th pitches and again their 60th to 70th pitches. The two peaks of the True RV line occur when starting pitchers are generally facing the 4th and 5th batters in the lineup.
-Relievers have better stuff than starters. The section from 1-15 pitches is composed mostly of relievers, and that's the lowest trough in the StuffRV curve.
-Those pitchers who managers leave in past the 100-pitch mark are well above average, and their stuff continues to be above average. I'll account for this survivor bias another time. For now, I'd rather do brief case studies of one pitcher who maintains his stuff throughout the game, and another who does not.
I correlated every pitcher's pitch count with his StuffRV on that pitch. Brett Anderson seems to pick up steam the deeper he goes into a game. I classified his pitches into four clusters: fastball, slider. changeup, curveball So the first thing I did was look to see trends in his velocity and movement. Well, nothing really stood out. His slider gains almost an inch in movement by the end of the game, but I don't think that's it. Then I remembered that Anderson's slider was the most valuable slider in baseball last year, and it edges out Zack Greinke's as the *nastiest* starter's slider in baseball by my rankings.
So there you go. He challenges hitters with fastballs the first time through the lineup and then switches to mainly off-speed pitches, which are his bread and butter. Hence, you might say, he improves his stuff as the game goes on.
Jered Weaver, on the other hand, has worse stuff by my calculation as the game goes on. Weaver throws his fastball 68% of the time in his first 25 pitches, compared to 52% from his 51st pitch on, and in exchange his changeup usage increases from 10% to 23%. Not only is there a difference in Weaver's pitch selection, but there's also a notable change in his pitch quality. Here are the characteristics of his fastball as the game goes on:
But pitchers who have a changeup as good as Weaver's don't rely on stuff to get by. Weaver's all about deception. And that stuff I don't know how to measure.