Chipper’s First-Pitch Aggressiveness by Pitcher xFIP by Dave Allen March 4, 2010 Yesterday, I looked at an exchange between Jon Sciambi and Chipper Jones concerning how often the latter swings at first pitches. Some commenters bristled at the idea of a broadcaster giving hitting advice to Chipper Jones. I don’t disagree with that take That was never Sciambi’s intention, and, anyway, what I found interesting about the interaction was more the idea that, when a player is confronted with these new metrics – especially a player as good as Jones – there is the possibility that his response can give us deeper insights into the game. Again quoting Jones’s response to ‘Duk: “There are certain pitchers, quite frankly, that you can’t get behind,” Jones said. “You want to be aggressive and the first hittable fastball that you get is the pitch you want to put in play. Because they’ll bury you if they get ahead of you. You can’t let them do that. So instead of saying, “He is swinging too often at the first pitch,” we can say, “Huh, maybe this is part of the reason for his success.” This take was well articulated by Tangotiger over at The Book Blog. Taking that tack we can look at how Jones approaches at-bats against different pitchers. Here I looked at the rate Jones swings at pitches in the zone separated out as first pitches and all others based on the opposing pitcher’s xFIP. Standard errors of the fit curves are indicated. The results are just as Jones said; against pitchers with a low xFIP, presumably the certain pitcher he was referring to, he is just as likely to swing at a first pitch in the zone as he is to swing at subsequent pitches in the zone. But against average-or-poor pitchers he swings much less often at first pitches in the zone than subsequent pitches in the zone. So Jones’s aggressiveness on first pitches is seen just against better pitchers. The obvious question is the extent to which other hitters show this same trend, and, if they don’t, how much it factors into Jones’s success. More generally, it raises questions about how hitters respond differently when facing good pitchers. The converse, how pitchers pitch differently to the good hitters, has been examined, but I am not aware of studies on this.