Pitching by the Numbers: Pitch counts

Let's look this week at young pitchers at risk for innings-limit concerns and examine what teams should be focusing on instead of innings, their total pitches thrown.

The idea is to put each young pitchers’ IP total in the league-average context of 16.4 pitches per inning (the average rate this year). If a pitcher is well under this P/IP average, he should be allowed to throw more innings (or at least be able to) before fatigue/injury concerns set in. If he is above the average, then his innings total will underrate his true workload, meaning he should be viewed as having pitched more innings than his actual innings total.
But first, I have some old business I'd like to address. Last week, we looked at isolated slugging allowed (slugging average minus batting average) to estimate a luck-neutral ERA. Typically, this is done with batting average on balls in play. Many respected colleagues discussed this column and the underlying theory with me on Twitter (@MichaelSalfino). The most sabermetrically inclined argued that ISO allowed generally correlates poorly year-to-year with pitchers and thus should be ignored for projection purposes. I stipulate that it does correlate poorly year-to-year, meaning there is a wide variance on average. But the pitchers who are extremely good at it absolutely do exhibit year-to-year consistency in ISO allowed, no one denies. Even relievers such as Mariano Rivera do it (15 seasons with an elite ISO allowed), implying that ISO allowed is not a stat that needs a full-season of data for starting pitchers (Rivera is a reliever who often generally throws 70 innings per season or less).
Put most simply, hitters mostly control outcomes in the hitter vs. pitcher matchup. It’s been shown to be about 60-40, generally, favoring the hitter. But greatness, even goodness, for pitchers is defined, I think, by the extent to which they swing this control in their favor. The elite pitchers clearly do this by limiting extra-base hits. That’s an outcome they are able to mostly control, year in and year out. The trouble is, it can take about four seasons before we can identify these pitchers for certain. So, maybe Matt Harvey, for example, is just really lucky at that right now. I think this is very unlikely, but it’s more possible for Harvey than for, say, Justin Verlander. But we can’t wait for years. So, my supposition is that the greater you are in ISO allowed, the more likely it is that you are in control. And, to be clear, this is a skill that pitchers seem to develop as their careers progress (Johnny Cueto being the best example). So, yes, most pitchers are at the mercy of the randomness of how hitters happen to hit when they face them and have little control over ISO allowed. But some are not. And those are the pitchers we want. I think ISO allowed, at a minimum, is a tool that helps us identify who these pitchers are. It's certainly better at this than BABIP.
Finally, I feel badly about recommending Carlos Villanueva last week based on ISO allowed and WHIP. He was lit up against the Rockies afterward and looks to be ticketed to the bullpen once Matt Garza is activated. But this column is about doing what the numbers tell you to do. And it wasn’t just ISO allowed this year that made Villanueva intriguing but also his performance in the AL last year, especially his K/BB rate. (And his starter stats last year were better than his relief stats.) I would recommend him again with the same data since the risk was so low, given his availability on the waiver wire in most leagues.
Now we look at workload the right way, pitches thrown and not innings. The chart is pretty simple: actual innings pitched, pitches thrown, pitches per inning, adjusted IP (IP if the pitcher threw the league-average number of pitches) and innings saved per 200 innings pitched (So Matt Harvey, for example, could throw 220 innings at his current rate of pitches per inning and have it really be 200 innings for an average pitcher, because Harvey has been that much more pitch efficient.)

If the Rays are smart, and they are, they may shut down Moore south of where his strict innings total suggests. Of course, Moore could get more efficient, too. But at this pace, 188 innings for him will really equal 200. Some of the pitchers like Kershaw aren’t even a concern with innings. I just put every pitcher 25 or under who currently qualifies for the ERA title on the list. Sale, Harvey and Fernandez are the pitchers who will benefit if their teams look at pitches because they will be allowed more innings. At his pitches/IP rate, 222 innings for Sale really equals 200 for a pitcher who is average in pitches/IP. For Fernandez, who won’t get anywhere near 200 in all likelihood, it would be 214.

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