Ivan Nova and the Strikeout

By most measures, New York Yankees’ starting pitcher Ivan Nova has had a very disappointing season. Although his record is 5-2, he has a 5.46 ERA, 1.57 WHIP, and has given up almost two home runs per 9 innings pitched. However, there is one aspect of his game that has dramatically improved from last year: his strikeouts.In both 2010 and 2011, Nova struck out about 14% of all batters that he faced. This year, he has struck out 22.6% of batters. To translate this into a more familiar metric, his K/9 the past two years have been 5.57 and 5.53 respectively. This year, his K/9 is exactly 9. No matter how you look at it, Nova is striking batters out at almost twice the rate he has done over his career. Why is this happening? Let’s take a closer look.

I’ll admit from the get-go that I am by no means a scout, nor have I seen Nova pitch much this year, so I am not basing this analysis on anything I am seeing from his delivery, mechanics, etc. Luckily, however, we have a world of data at our fingertips, and while this cannot replace good scouting, hopefully I can still get a sense of some of the factors leading to Nova’s increased strikeouts.

The first thing I like to look at is SwStr%, or whiff rate. Simply, this is the percentage of all pitches that batters swing and miss on. In general, a pitcher’s whiff rate correlated fairly strongly with a pitcher’s strikeout rate, although there are some pitchers that rely on called strikes for strikeouts (see Bartolo Colon). So over a small sample size, if a pitcher has an increased strikeout rate but their whiff rate has stayed the same, there is a good chance that they are just getting lucky, and their strikeouts will regress back to previous levels. With Nova, however, we see a greatly increased whiff rate this year compared to years past. In 2010 and 2011, batters swung and missed at 6.6 and 6.8% of pitches Nova threw, but this year, they have swung at 9.1% of pitches. Although this is still just above league average (8.8%), it is a dramatic increase from his career numbers, and indicate that his jump in strikeout rate is not a fluke.

How is Nova getting batters to whiff more often this year? Often a jump like this is best explained by an increase in velocity, yet Nova’s fastball velocity (92.7 mph) is just about on par with his career (92.6). But if we look at Nova’s pitch selection this year, we can see a significant change in his approach. Last year, Nova relied much more on his fastball, throwing it about 61% of this time. This year, however, he has thrown a fastball only 51% of the time. What is he throwing instead of those fastballs?

The answer: sliders. Last year, 13% of Nova’s pitches were sliders, and in 2010, he only threw it 2% of the time. But this year, Nova has thrown his slider a remarkable 19% of the time. And for good reason, because batters are whiffing on a stunning 21.34% of Nova’s sliders. This is basically on par with how batters have fared on his slider for Nova’s career, but for some reason, Nova decided to throw it more often this year. And it’s working. With the increase in sliders, Ivan Nova is making batters swing and miss and consequently getting more strikeouts. The great news is that this isn’t affecting Nova’s control, as he’s walking fewer batters than ever. Though Nova’s performance in 2012 has been disappointing, he has been a more dominating pitcher as far as the strikeouts go. If he can control the hits and the long ball, he should be a solid starter moving forward.

Stats taken from Fangraphs.com and brooksbaseball.net