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Are Hitters More Aggressive on First Pitches from Good Pitchers?

Last week I looked at Chipper Jones‘s first-pitch aggressiveness. This aggressiveness is a little surprising because Jones has extraordinary plate discipline, with more walks than strikeouts in his career. Jones explained it as a way to not get behind good pitchers. It turned out this was the correct, as Jones swung more often against first pitches in the zone from low-xFIP pitchers than high-xFIP pitchers. On subsequent pitches in the zone this relationship was lost and he swung at a relatively constant rate.

This result led to a number of natural questions the two most pressing: how does this compare to other hitters and how much of a role does it play in Jones’s success?

Here I address the first question. I repeated the graph from Thursday for all batters rather than just for Jones. That is, I looked at the Z-Swing rate (swings at pitches in the zone) for first pitches and subsequent pitches based on the pitcher’s xFIP. The curves are below with standard errors indicated. For comparison, I added Jones’s curves as dotted lines but omitted his standard errors to keep the graph from being too cluttered.

There is a striking difference. The average hitter swings much less often at first pitches than all others, but with no discernible trend based on the quality of the pitcher. This is very different from Jones’s first-pitch curve, which drops off rapidly as the pitcher xFIP increases. On subsequent pitches, the average hitter’s swing rate increases compared to his first-pitch rate, but again has little relationship with the xFIP of the pitcher. Here, Jones is not different than average.

So it looks like the average batter is not making the same effort as Jones to not get behind the best pitchers. This is surprising. I thought we would have seen this trend — just to a lesser extent — with all hitters, but that is not the case. Tomorrow I will look at the effect this has on at-bat results.