I was listening to yesterday’s excellent FanGraphs Audio with Carson, Jack and Matt, and they brought up Edwin Jackson. In the episode, they noted Jackson’s soaring O-swing rate last year; wondered whether that had to do with his increased slider percentage; and also considered his strikingly good pitch-value numbers on his slider versus the poor ones for his fastball, in spite of that fastball’s blazing, fourth-fastest 94.5 MPH average speed. I thought those interesting observations warranted further investigation.
First off Jackson is effectively a two-pitch pitcher, rare for a starting pitcher. To RHBs he throws his fastball 60% of the time and slider 37%. Righties rarely see his curve or change. Against LHBs he throws these tertiary and quaternary offerings a little more often, but not by much, going with his fastball 67% of time and slider 20%. So even LHBs see a fastball or slider nearly 9 times out of 10.
As Matt noted, his slider percentage increased last year, from roughly 20% in 2006-2008 to 27% in 2009. This is the big reason for his increased O-Swing%. His out-of-zone sliders get swung at 37% of the time versus 26% of his out-of-zone fastballs. (These are for the pitchf/x zone, which is a little bigger than the BIS zone used for our plate discipline section, so these numbers do not correspond perfectly). The increased use of the slider neatly corresponds to his increased O-Swings.
Like most pitchers, Jackson throws his slider more often when he is ahead and less often when he is behind in the count. In these situations there was little change in slider use in 2009. The increase in sliders came early in at-bats: in 0-0, 1-0, 0-1 and 1-1 counts Jackson threw almost a third more sliders in 2009 than previously, which accounted for the majority of the increase. So it looks like Jackson was more comfortable going to the slider earlier in at-bats and even often starting off with one.
Finally what is going on with his fastball? It seems like dialing up the speed is just not enough. On the average fastball a batter misses with 14% of his swings, against Jackson’s fastballs just 12%. And when the average fastball is put into play, it gives up a slugging of .521, but Jackson’s is .556.
Almost all pitchers need to throw a fastball at the very least 50% of the time to keep batters honest and get strikes, but it would be interesting to see whether Jackson can continue to decrease his fraction of fastballs and increase his fraction of sliders. His 27% in 2009 was already 6th most in the Bigs, but maybe he can push it north of 30% as Ryan Dempster and Brett Anderson have.
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