Can Ivan Nova survive with two pitches?

Ivan Nova has had a rollercoaster of a year, bouncing all over the team's depth chart in less than two months. He started with a strong spring training bid for 5^th starter, but fell short when the Yankees chose CC Sabathia instead. Nova was demoted to a bullpen spot, but didn't have a defined role and saw limited usage. Injuries to CC Sabathia and Luis Severino earned him a temporary job in the rotation, and he's made three excellent starts since.

Nova's place on the Yankees has been constantly tinkered with, and so has his arsenal on the mound. He started his career with a four-seam fastball, curveball, and changeup, eventually developing a sinker and slider. For a time, Nova had six pitches, but has phased out his changeup and slider over the past couple seasons. It's hard to explain just how much change his usage rates have undergone, though a graph does it some justice. 

Nova's always been a fan of the curveball and its whiff-inducing abilities, which explains why it has been the only constant in his repertoire over the years. He's gradually fallen in love with the sinker given its elite groundball rate, and has fallen out of favor with the four-seam fastball that is seemingly never swung at. The changeup has always been pounded, so throwing that away makes sense, while the slider was okay in the past but doesn't really move much. This leaves him with just two pitches that he's really comfortable throwing—the sinker and curveball—as he's only using the four-seamer about six times per start. Despite the past usage turmoil, Nova has found a pitch mix he likes as a starter.            

Note the KCA@NYA game, or when Nova made his first start of the season. Although there hasn't been a massive change between his cumulative relief appearance usage and starting mix, he has found consistency as a starting pitcher that wasn't there as a reliever. We can probably expect that to stay stable going forward, meaning we're now looking at a pitcher that throws the sinker at a 61% rate, a curveball a quarter of the time, and a four-seamer about 8% of the time.

What you probably noticed by now is Nova is predominantly a two-pitch starter. Sure, there's the occasional four-seam fastball, but Nova will fill his starts with a sinker and a curveball. This shallow arsenal of Nova's could be his fatal flaw as starter. One of the tell-tale signs of a reliever is when the player lacks a usable third pitch, and Nova fits that criteria. However, given his early success, we've been forced to reevaluate the two-pitch rule.

To determine whether Nova can start—and thrive—with two pitches, I first looked at precedent. If another starter could defy the expectation of having at least three pitches, maybe Nova could too. As a general view, I took the 15 pitchers that used just two of any type of fastball, slider, changeup, curveball, or other pitches more than 10% of the time (min. 100 IP) in 2015.

**Nova's data is for 2016

The first thing you'll notice is that there are actually some really good pitchers listed. That said, this table can be a bit misleading. I included these specific pitchers for simplicity's sake, but a lot of these pitchers have multiple versions of each type of pitch (like Nova's four-seamer and sinker) that make them more than two-pitch pitchers. When looking at which of these pitchers really do use just two pitches, I came up with nothing. To put it plainly, there wasn't a two-pitch starter in the big leagues last season. Still, there are a couple of names worth looking at in this crop.

The first pitcher is Gerrit Cole, one of the best starters in the big leagues. Cole throws his fastball about 68% of the time, his slider about 17%, and his curveball about 10%. He's clearly got three pitches (or more, depending on how the fastball is classified), but Cole's case can help us learn something about Nova. The Pirates' ace has two elite offerings in his fastball and slider that have allowed him to remain in the upper echelon of starters despite a shallower-than-usual repertoire. Whether or not he'd be able to succeed without the curveball is up for debate, but there is an argument to be made that a two-pitch starter could exist if they had two plus-plus pitches like Cole.

This brings us to a name not on the table because of his innings total—Vincent Velasquez. Velasquez has been one of the biggest breakouts this season, being a dominant starter next to Aaron Nola at the top of the Phillies rotation. Velasquez is primarily a fastball/curveball pitcher, only occasionally mixing in a changeup (about 8.3% of the time). He, like Cole, has a pair of dominant pitches, but mixes in his third offering even less than Cole does. While a league adjustment and shallower repertoire could cause him trouble in the future, Velasquez does make a case for being a two-pitch starter with two top-end pitches.

The problem for Nova is that he doesn't have two elite offerings. The sinker boasts a high groundball rate, but isn't whiffed on much and was hit well to the tune of a .456 slugging against last season (and .353 in 2016). The curveball is a good bat-missing pitch, but has been tattooed this season with a .790 slugging against. That should improve, but the pitch has less drop this season and may not be as hard to hit as in the past. We're looking at two solid pitches from Nova, but definitely not elite ones.

The last pitcher to mention is Taylor Jungmann. Jungmann also uses a four-seam/sinker combination along with a curveball at similar frequencies, though the four-seamer dominates his repertoire in the same way Nova's sinker does. Jungmann also uses a changeup, though it's thrown very rarely. They're far from a perfect match, but Jungmann is at least comparable to Nova.

Jungmann was good in his rookie year, though he fell down to earth this year and was a disaster before being sent to Triple-A. That's not promising. Not only is there just one (almost) two-pitch starter in the big leagues other than Nova, but that one pitcher has been terrible this season. Proclaiming that Nova will be bad because Jungmann was bad and almost was a two-pitch pitcher is silly, but the fact that there is only one other pitcher that can almost be qualified as throwing just two pitches is extremely discouraging.

I don't think anybody expected Nova to continue to be lights out as a starter, but there is some faith in him being a reliable arm in the Yankees' rotation. While it's not out of the question that this happens, consider me extremely skeptical. Nova relies on two pitches and there wasn't really a two-pitch pitcher in the majors last season. The only one that came close was lit up this season and is back in the minors. There's a chance Nova can be one of the few starters that can succeed with just two pitches, but the chances of that happening are slim. Maybe it's not time to start demanding Michael Pineda and Luis Severino be sent to Triple-A, because trusting Nova over a full season probably won't go well.