A Last Look at First-Pitch Aggressiveness

Wrapping up my series on first-pitch aggressiveness I am ready to address the second question I put froward in Monday’s post: to see whether it first-pitch aggressiveness against good pitchers pays off. Before I do that, though, I want to address a suggestion from the comments section of Monday’s post who wanted to see Monday’s chart broken up by batter quality.

I took Tango’s suggestion:

Right, what the others have been saying. Chipper is a career .400 (wOBA) hitter. I’d rather see five charts with the breakdown at those levels:
.380+ hitters
.350-.380
.320-.350
.290-.320
under .290

Here are the z-swing rates for these five groups of batters for first pitches and subsequent pitches by pitcher xFIP. The color of the line indicates the group with the lightest gray the worst hitters and black the best. The dotted lines are for first pitches and solid for all others.

Sorry that the graph is a little cluttered, but that is the point. There is noclear relationship, if I had included the standard errors for these lines the five first-pitch ones would overlap completely and the five subsequent-pitches ones would as well. All five groups have pretty much the same swing rates and no clear trend depending on the xFIP of the opposing pitcher. So Jones’s first-pitch aggressiveness against good pitchers is unique compared to not only the average batter, but also compared to his peer group of very good batters too.

Ok now we can turn our attention to how this behavior affects the result of an at-bat. I break at-bats into one of four groups: those with first pitches in the zone and swung at, in the zone and taken, out of the zone and swung at, and out of the zone and taken. For each group I calculate the wOBA of the at-bat and plot against the pitcher’s xFIP. Color indicates whether the pitch was in the zone, black in the zone and red out. Line style whether the pitch was swung at, solid swung at and dotted taken.

First look at the first pitches out of the zone (red). There is a huge difference, no matter at the quality of the pitcher, in the result of at-bats when these pitches are swung at or taken. The difference between starting an at-bat 1-0 versus out-of-zone contact or starting 0-1 is great, even against poor pitchers. I think this goes a long way in explaining batter’s low swing rates on first pitches. Batters cannot tell for sure whether the pitch will be in the zone, and better to not swing.

On first pitches in the zone there is not quite as much difference, but the size of the difference expands as the pitcher gets better. So not swinging at a first pitch in the zone against a good pitcher results in a great deficit (versus swinging at it) than not swinging at a first pitch in the zone against a poor pitcher. This would suggest that swinging at first pitches more often against good pitchers is a good idea. But only if you have a good idea whether the ball will be in the zone or not, because the disadvantage of swinging at a first pitch out of the zone is just so great.

I think this is the reason Jones is well poised to exploit this difference and swing so often on first pitches against better pitchers. Few batters have his ability to swing at balls in the zone and not those out of the zone.