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Entries in knuckle curve (1)

Tuesday
Aug232011

Breaking Down A.J. Burnett's Zones

So now A.J. Burnett may really lose his spot in the Yankees rotation. I wanted to see if there was anything he's done this season that may provide hope that he could bounce back. When I broke down the zone location to up, middle and down, I found something pretty interesting.

First, the bad:

2011 A.J. Burnett - Up in the Zone

Basically the middle of the strike zone includes any pitch that hits the middle seven inches of the zone (which is normalized depending on the height of the batter). So anything above the top of that seven inch mark (whether inside or outside the actual strike zone) is designated as 'up'. The same applies for pitches down in the zone which you will see further down in the post.

This season, A.J. ranks in the bottom 21% of the league in opposing batting average (.271) on pitches up (min. 500 pitches thrown in that zone). The league average is .240. His opponent slugging percentage of .474 ranks in the bottom 11% of the league and is nearly 100 points worse than the league average. Sadly, this is actually an improvement over last season when he ranked in the bottom 5 and 3 percent of the league in opponent average (.318) and slugging (.588) respectively.

2011 A.J. Burnett - Middle of the Zone

When throwing over the middle of the zone, Burnett has not only been flat out terrible, he's basically been the worst pitcher in the league. He ranks second to last in opponent batting average (.379), and dead last in opponent slugging percentage (.707), opponent wOBA (.452), and HR/FB (23.3%).


Yet, here's how he's done on pitches down in the zone:

2011 A.J. Burnett - Down in the Zone

As bad as A.J. Burnett has been throwing middle and up, he's been that awesome on pitches down. Batters are hitting just .117 against him in 259 plate appearances decided on a low pitch (1162 total pitches), which is the best in baseball this season. Opponents are also slugging just .157 on low pitches, which also leads the league.

Most of this success on low pitches is probably due to his knuckle curve, which has been by far his best pitch this season (and has accounted for 50.9% of his low pitches). Opponents have a .188 wOBA versus his curve this season compared to a .407 wOBA against all of his other pitches. Burnett obviously can't rely on just one pitch, and we're seeing that quite clearly this season. The decline of his fastball is probably the biggest culprit here, as hitters are putting up a .439 wOBA against it, ranking him in the bottom 1% of the league (Only Edinson Volquez and Kyle Davies have been worse with their fastballs). That number has been increasing every year since PitchFX data began keeping track (2008: .364, 2009: .385, 2010: .403).

His stuff is simply getting worse. Maybe moving him to the bullpen will help him regain something, but is it best for a Yankees pen that has been exceptionally good this year?