Aaron Nola’s Return Upgrades the Phillies Rotation
The Philadelphia Phillies have had terrible pitching this year. I have already addressed how there isn’t any immediate help on the way for the bullpen (though with speculation that Ricardo Pinto is moving to the bullpen that could change). Where there is immediate help for the Phillies is in the starting rotation. The Phillies did not win Aaron Nola’s first start back from injury, but he did show that the Phillies may have made a significant rotation upgrade.
There are a lot of unknowns around Aaron Nola’s future. The most significant is his health. So far this year, we have had no reason to doubt that Nola’s arm is fully healthy, but it is reasonable to be unsure whether he will hold up over a full season. Then there is his back injury which held him out for a month (with two rehab starts). Once again Nola looks healthy, but with some setbacks along the way, it is hard to feel completely comfortable. For someone now in his 3rd MLB season, Aaron Nola has thrown very few innings, both due to injury and a quick path through the minors to majors. This gives us very little baseline of performance.
What we do know about Nola this year, amounts to a couple of things. The first is that his velocity is up. By Brooks Baseball’s velocity measurements (these should be normalized for park, weather, etc) Nola’s velocity is up over a mile per hour across all of his pitches. This takes Nola up from sitting about 91.5 to about 92.5. This all moves up the lower end of his range and gives him an upper range to blow past batters. The second is his ability to generate ground balls is intact. As fly ball rates and home run to fly ball rates rise, keeping the ball on the ground continues to be the best way of avoiding big damage.
What we also know about Aaron Nola is that over 211.2 career innings, various metrics have very different opinions of him and what he is to the Phillies. By ERA he is at 4.21, which gives him a career bWAR (RA9 WAR) of 2.4. By FIP and Fangraphs he is at 3.43 and 4.3 fWAR (FIP based). Baseball Prospectus has yet another opinion, their pitching metric DRA loves Nola to the tune of 3.10, giving him a career WARP of 5.3. There are three seasons of data going into those numbers, including two injuries and a rookie season that was good but not great. I have broken out his three years, separating Nola’s good half and bad half last year, as well as taking out his injury game this season.
|2017 (w/o injury)||3||18||2.5||25.0%||5.5%||0||59.2%||3.11||2.57|
*DRA and FIP are for the full season when shown and include Nola’s injured start in 2017
Before talking about what this means for Nola’s potential future, I want to briefly talk about what ERA, FIP, and DRA all tell us. ERA doesn’t care about luck, like Nola’s 60.6% strand rate in 2016 or that he had a .334 BABIP while also having a high ground ball rate. FIP does a little bit better in narrowing down the luck, but like DRA (which we will get to) it does not know how to deal with a pitcher who is putting hittable pitches over the plate, like Nola was doing during his last 8 starts of 2016. FIP also has no knowledge of Nola’s ground ball profile outside of the home run suppression. DRA is the most optimistic because it does know about the ground ball rate. It also knows the Phillies play in a hitter friendly park and that their OF and catcher defense was not great in 2016. However, it does not know that some of Nola’s struggles and “unluckiness” in 2016 were because he was putting balls over the plate that weren’t being hit for home runs, but they were being hit for sure hits all over the ballpark.
The truth of what Nola is, is probably somewhere in the middle of all of these metrics. He is unlikely to be the guy he was to open last year, a fact we knew at the time. However, he is showing in a small sample this year that he can be a really good pitcher. So far in his career, he has shown that he can strike out batters at a good rate, limit walks, limit home runs, and keep the ball on the ground. Those are the fundamental pieces of a good pitcher. His increase in velocity gives him some more wiggle room to lose a little for a start or stretch of starts without becoming ineffective. The big remaining question for Nola is health, and we are never going to know, because he is a pitcher, if he is going to stay healthy. For now, the Phillies needed help in the majors, and they just got their best starting pitcher back, and that is a good thing in a year without good things.