When the Yankees signed Hiroki Kuroda to a 1-year deal this offseason, they figured that they were getting a solid #3 starter who would keep the ball on the ground, get a decent amount of strikeouts, and keep the walks under control. Some regression in Kuroda’s impressive numbers for the Dodgers could have been expected, due to both his advancing age and his transition from a pitcher-friendly park in the National League to the friendly confines of Yankee Stadium and the AL East. While there have been some bright moments from Kuroda so far this season (particularly his 8 innings of shutout ball against the Angels), his overall performance has been somewhat disappointing.
On the season, Kuroda is 3-5 with a 4.50 ERA (5.28 FIP, 4.21 xFIP). A disparity between ERA and FIP could be explained by a number of factors, including BABIP, strand rate, home run rate, walk rate, and strikeout rate. For several of these factors, there is not much of a difference. In Kuroda’s 2012 BABIP of .287 is not especially high. Indeed, it is exactly equivalent to Kuroda’s 2011 BABIP. Kuroda’s strand rate of 74.9 percent is 5 percent lower than his 2011 performance, also not a major difference. These factors don’t appear to have much explanatory power in this case.
Where we do see big differences are in Kurdoda’s peripherals, namely, strikeout rate, walk rate, and home run rate. Kuroda has fanned 1.6 fewer batters per 9 innings this year than he did in 2011 (7.2 to 5.6), a major drop that seems too big to be explained solely by a league shift. While the strikeouts are down, Kuroda’s walk rate has jumped, by about 1 batter per 9, going from just over 2 bb/9 in 2011 to over 3.19 in 2012. Kuroda’s current walk rate is not a big problem (compared to the dropping strikeout rate, per se) but the fact that both of these figures have moved in the wrong direction is a worrying sign.
As we have seen from several other Yankee starters this season, Kuroda’s home run rate has skyrocketed in 2012, increasing by more than 50 percent from 2011. Interestingly, Kuroda is giving up fly balls at a slightly decreased rate, but many more of these flyballs are leaving the yard in 2012 (18.8 percent) compared to 2011 (11.3 percent). This could be attributed to some combination of bad luck, a hitter-friendly home park, and harder-hit balls, but the latter is likely the primary reason for such a significant disparity.
Since we have already established that Kuroda is giving up many more home runs despite relatively constant groundball and flyball rates, the next step is to see if his raw stuff has declined at all. If so, this would also be a reasonable explanation for his lower strikeout rate. Indeed, there are some notable changes in Kuroda’s stuff. Per Brooks Baseball, Kuroda has lost about 1 mph on his 4-seam fastball, going from an average of 92.68 in 2011 to 91.49 in 2012. Although his slider and splitter have more or less maintained their velocity, they have each lost a few inches of vertical movement, possibly making them more hittable pitches.
Kuroda’s pitch mix has also changed substantially in 2012, perhaps to compensate for his decreased 4-seam velocity. He threw the 4-seamer about 23 percent of the time in 2011, and is down to just 12 percent in 2012. The sinker, his bread and butter pitch, has remained relatively constant in usage and velocity. Kuroda has made up for the decrease in 4-seamers by throwing more breaking balls, throwing the slider 9 percent more often than he did in 2011 (30 compared to 21) and the curveball 5 percent more often (3 percent to 8 percent).
As Kuroda’s velocity and pitch usage has changed, so have their outcomes. His whiff rate decreased with his 4-seamer, sinker, and slider, though it is slightly increased in the curveball and splitter. The biggest change is in the 4-seamer, which decreased from nearly 11 percent in 2011 to almost 7 percent in 2012. This finding seems consistent with the decreased 4-seam fastball velocity that has been observed thus far.
What can we interpret from all of these findings? One is that Kuroda appears to be losing some 4-seam fastball velocity, and is compensating by increasing his breaking ball usage. While I don’t have the home run data broken down by pitch type, it is plausible that home runs are more likely on breaking pitches (if anybody has data supporting or refuting this, please let me know). It is also possible that the loss of velocity and movement on several of his pitches is responsible for the increased home run rate and lower strikeout rate. It is also possible that some combination of adjustment to the AL and warmer weather over the summer will allow Kuroda to get his velocity back and improve his performance.
There is no easy fix for Kuroda’s home run problem, but further tinkering with his pitch mix could have some impact. Kuroda may not be able to fully compensate for his reduced raw stuff, but the fact that he has 5 different pitches that he is comfortable throwing in a variety of counts certainly can work in his favor. Ultimately, I find it hard to believe that his home run rate will stay this high all season, and as that rate drops, Kuroda’s performances will start to look better.
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4 Responses to What’s different about 2012 Kuroda?
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TIQ IQ
Is there month-by-month data on home runs/fly ball rate at the new Yankee Stadium? I seem to recall that the stadium had been giving up more homers early in past seasons than late.
For whatever its worth, Kuroda appears to be a slow starter for his career. His career ERA is about a half a run less in the 2nd half of the season than the first half and his career K/9 is 6.0 in March/April and 5.7 in May. He’s also been more homer prone in the first half with over 1 hr/9 in March – June vs. .5/9 in June and .6/9 in August.
That’s worth knowing.
how about n. l. west to a.l. east