According to MLBAM pitch classification, last year Barry Zito threw 681 curveballs, accounting for 22 percent of his pitches. This year he has thrown 499 of them (as of Sept. 4)— that is 18 every 100 pitches. The big drop has occurred against left-handed hitters, who used to see a lot of Zito’s deuce, nearly 30 percent; this year, they have been fed it at a 16 percent clip.
The following graph depicts Zito’s curveballs (2008 version) by their movement.
You don’t need a software that performs cluster analysis to notice that there are two distinct types of pitch in the above plot—you don’t even have to know what cluster analysis is, for that matter. Separating those two pitches looks as easy as putting the curves with a vertical movement greater than minus five in one bucket and the remaining into another one. If you calculate the average speeds, you get 77 mph for bucket one and 71 mph for bucket two.
So Zito used (in 2008) two different curves: one faster, the other with more vertical break. This is consistent with his scouting report at 60 ft 6 in, that states “A couple years ago he added a tighter breaking ball that he uses like a slider to LHs”. The reference is to his 77 mph curve, that I’ll call the hard curve from now on (as opposed to the slow curve).
Last year, Zito delivered 202 curveballs to left-handed batters, 98 of them (49 percent) of the hard kind. He also used the pitch against righties, but to a lesser degree (123 of 479 total curves, 26 percent).
Let’s look at the curveball scatter plot for 2009.
It’s gone! Zito is not using the hard curve anymore, save for an occasional pitch here and there. He throws the slow one with the same frequency he did in the past—15 percent to lefties (identical to 2008), 18 percent to righties (3 percent more than last year).
To make up for the discarded pitch, he is using a slider extensively for the first time in his career. According to MLBAM classification algorithm, he used to throw one slider every 100 pitches; now he is using it 13 percent of the time. FanGraphs has different values (from 10 percent to 19 percent), but I’ll stick with MLBAM’s because with them I’ll be able to present lefty/righty splits.
His new weapon is used mostly against left-handed hitters, the same target that used to be fed the extinct hard curve. Zito delivers the slider once every four pitches against lefties, and once every 10 to righties. Other than filling up the void left by putting the hard curve in the closet, the new pitch is eating up some of the change-up share: both left-handed and right-handed batters have seen a drop of 10 percentage points in that pitch, meaning that the former are hardly seeing it anymore.
Nick Kapur at UmpBump wrote, at the All-Star break, that the slider gives Zito “another option to get a strike over without always having to groove his 86 mph fastball right down the pipe”. That seems to be hardly the case, since the slider is the pitch Zito is throwing less over the plate (41 in-zone percentage). And that’s for a reason, since batters are chasing the pitch out of the zone (42 percent swings on balls).
In fact, Zito is placing the other pitches more frequently over the plate: The change-up, now used only versus opposite-handed batters, has gone from a 42 in-zone percentage to 47, the fastball from 40 to 44, and the slow curve from 46 to 51. Moreover, batters used to chase the slow curve out of the zone 20 percent of the time; this year they are fishing a lot more, at a 31 percent clip.
As a result, Zito is falling behind in the count less frequently this year: he has decreased the 1-0 counts by nine percent and the plate appearances in which he goes on three balls counts by six percent, while increasing by the same six percent the PAs where he goes on two strikes counts.
Okay, Barry. Now learn another pitch for right-handed batters during the offseason and you’re back to Cy Young form!
References & Resources
PitchF/x data from Sportsvision / MLBAM.
Barry Zito’s secret weapon by Nick Kapur @ UmpBump.