Since coming up from Triple-A in late June, Ivan Nova has pitched brilliantly with a 2.04 ERA, 8.63 K/9, and a 4.23 K/BB over 57 1/3 innings. He has picked up the slack of a struggling CC Sabathia and served to provide a solid 1-2 punch with Hiroki Kuroda for the Yankees rotation. Determining whether he is simply on a hot streak due for some serious regression or if he has turned a corner is difficult. But first, since these are so much fun:
Through Age 26 season
Pitcher A: 443 2/3 IP, 6.5 fWAR, 7.18 K/9, 3.27 BB/9 and 2.20 K/BB
Pitcher B: 457 2/3 IP, 6.1 fWAR, 7.04 K/9, 3.05 BB/9 and 2.31 K/BB
Pitcher C: 797 1/3 IP, 11.1 fWAR, 6.40 K/9, 3.43 BB/9 and 1.87 K/BB
Pitcher B is Ivan Nova with a chance to increase his statistics over the last two months of this season. Pitcher A is Cliff Lee and Pitcher C is Chris Carpenter. I'll explain why that's important later, but before I do that, let's discuss how much luck has played a factor for Nova this season.
Luck can show up a few different ways. We can look at FIP and compare it to ERA; if the FIP is higher than the ERA, the ERA is probably a little lucky. Nova's ERA and FIP are nearly identical at 2.93 and 2.91, respectively, so no luck factor there. Next we can look at BABIP, which is usually around .300. Nova's BABIP this year is .326, indicating he has been slightly unlucky on balls in play this year.
There are a couple competing factors. Nova's HR/FB rate this year is only 7.1%, lower than his career rate of 11.6% so there is some luck there. However, even with his low HR/FB rate, his xFIP, which considers a league average 10.5% HR/FB rate, is still a low 3.22 on the year. The one stat that seems unsustainable is his runners left on base, currently standing at 80.3%. That number is likely to go down, allowing a few more runners to cross the plate. Given the evidence on the whole, it's fair to say that Nova has not been overly lucky or unlucky this season. He has simply pitched very well.
To say that Nova has pitched well without a lot of luck only answers part of the question. What we really want to know is if this can continue. He has never been this good. What has changed? His main problem last year was the long ball as he gave up 28 home runs. When he was pitching well in 2011 and this season he was giving up homers at a much lower rate. His ground ball percentage in those years was around 53% compared to 45% last year. Watching Nova's starts, the movement on his fastball this season is evident and that naturally leads to more ground balls, thereby limiting home runs.
The main change Nova has made this year as opposed to prior years is in pitch selection. He is still throwing a majority of fastballs, but he has greatly increased the use of a two-seam fastball. The two-seamer has a natural sinking action which leads to more ground balls. Throwing the two-seam fastball has turned his fastball from a negative value pitch to an average pitch while maintaining the success of his curveball. The other change has been scrapping his slider which had not been overly useful.
Returning to Pitchers A and C from above, both Carpenter and Lee had similar beginnings to their careers. When more successful later on their careers, both pitchers induced ground balls using a sinking fastball and a cutter. Nova has the sinking fastball, but not a cutter. Cutters induce both ground balls and swings and misses. While Nova has been successful this year abandoning his slider, which was formed as a failed cutter, he might want to spend more time in the offseason working on a cutter if he wants to move into the ranks of the elite. This discussion seemed unfathomable three months ago (something nobody could have predicted), and that is a testament to Nova's willingness to adjust and try new things. Adding a cutter may turn 2013's hot streak into 2014's breakout starter.