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Aaron Nola’s Sneaky Overhaul

Written by: Justin Choi (@justinochoi)

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A lot of what was achieved by players during the shortened 2020 season is, unfortunately, statistical noise.

For example, although Jose Abreu won the AL MVP award, FanGraphs projects him to put up 1.9 WAR across a full season in 2021. In times of uncertainty, track record matters. Abreu is a 33-year-old first baseman who’s been roughly above-average throughout his entire career. The projection does make sense. 

But what if someone made genuine improvements in just 60 games? Many believe that Trevor Bauer is an example of such a player. And sure, we could discuss Bauer, but enough about him! Today, I want to shine the spotlight on the Phillies’ young ace, Aaron Nola. 

Nola had a fantastic season in 2020, but he was less-than-fantastic season in 2019 after posting a controversial—yet still fantastic—campaign in 2018. Based on this track record, you could predict that his 2020 is a slight ‘up’ preceding an eventual ‘down’. Sure, maybe that’s what will happen. But digging through the numbers has led me to believe otherwise –– because of how he’s overhauled his pitch repertoire. 

This first change, though, is perhaps not so sneaky. This simple chart from Baseball Savant shows what I mean: 

That’s a complete renovation if I’ve ever seen one. The two pitches that allowed the loudest contact have been thrown less to make room for his changeup and sinker. When your four-seamer and knuckle curve consist of two-thirds of your home run total (18 of 27), it’s probably a good idea to dial back on them. 

But while simply throwing fewer problematic pitches helped, what’s more intriguing is how Nola refined them. 

A common problem with Nola’s fastball and knuckle curve was pitch location. Too often did they end up in the heart of the strike zone, which is a surefire recipe for hard contact. Here are two heat-maps, one for each pitch, which illustrate what I’ve explained so far: 

The red is concentrated in the mid- and lower-third of the strike zone –– not good. With those images in mind, however, consider how the heat-maps have changed for the 2020 season: 

What has Nola done differently? Rather than alter the movements of his pitches, he simply optimized their usage. His fastball, which has both terrific arm- and glove-side ride, becomes more lethal when it lands in the shadows of the strike zone. Consider how in 2019, the pitch didn’t venture much outside the zone, whereas in 2020, it’s clear that Nola is exploiting the edges and getting hitters to chase. The whiff rate on his four-seamer, which has shot up from 19.3% to 29.1%, needs no further elaboration. 

To provide contrast, Nola buried his curveball increasingly often in 2020. Again, there isn’t much difference in terms of spin axis and/or vertical movement, but just keeping the pitch away from the zone has done wonders. 22.5% of Nola’s curveballs resulted in a swing-and-miss, the 5th-highest rate amongst pitchers who threw at least 100. 

Another subtle advantage this new curveball has created is the capacity to crush right-handed hitters. This is where small sample size does make the results hazy, but the difference is too significant to ignore: 

Look at that strikeout rate! We know the curve is leading the charge, as it produced 44.1% of his 59 punch-outs against RHH last season. The pitch’s own improvements helped, but we can’t ignore the synergy it has with the four-seamer. When the two worked together flawlessly, hitters had zero chance of survival: 

Next, Nola made the bold decision of anchoring his changeup as the centerpiece of his repertoire. The pitch did have the lowest xwOBA in his repertoire in 2019, but he’s somehow managed to raise the bar. To describe its awesomeness, I’ve admittedly done some cherry-picking that I swear is not too egregious. I’ll explain as I go. 

In 2020, Nola’s changeup allowed an average exit velocity of 82.5 mph. It also produced a swinging-strike rate (SwStr%) of 19.7%. Both are well above the league-average changeup. But how rare is this two-fanged force of contact suppression? 

To find out, I limited my sample to pitchers who threw at least 200 changeups. From there, I picked out of pitchers whose changeups allowed an average EV of 83 mph or less and generated a SwStr% of 20% or more. Yes, I’m rounding Nola’s rate to the nearest whole number, but I warned you about the picking earlier –– it’s too late to stop me! And in my defense, there’s virtually no difference between 19.7% and 20% when describing a couple hundred pitches. 

Anyways. Without further ado, here’s the elite company Nola joined: 

It’s worth noting that Zach Davies and Kenta Maeda missed the cutoff by 0.1 mph, and their SwStr% would have been higher than Nola’s. Still, Nola’s inclusion shows that his changeup was one of baseball’s best. Though our scope is limited to 12 games, it isn’t completely bonkers to suggest that Nola’s changeup may have been elevated from merely a great one to a brilliant one. 

Plus, there’s evidence to support the idea that Nola’s changeup is different than before. The movement profile of a pitch matters, but we also consider how it works in conjunction with other pitches. For example, a regular changeup and curveball which have markedly different movements are, together, more effective than a wonky, zig-zagging changeup and curveball which move like crazy but have similar spin rates, spin direction, and so on. You can’t fool a batter without creating separation. 

Consider, then, how the movement of Nola’s changeup has changed in relation to his other pitches. Here’s 2019 and 2020 side-by-side. See if you can spot the difference: 

Compared to 2019, Nola’s changeup retained its horizontal movement and gained an inch or two of vertical drop. There’s now a clear separation between his sinker and changeup, and overall, his arsenal has acquired four distinct ranges of movement: 

From a pitch design perspective, this is ideal. In 2019, although the changeup and sinker differed in velocity, their similarities in movement meant the desired effect of pitch variety, deception, was not properly achieved. It’s worth noting that the existing velocity differential has also increased –– the velocity on his sinker has dropped by only hair, from 92.2 to 91.7 mph, whereas the velocity on his changeup has gone down an entire tick, from 85.8 to 84.9 mph. 

The separation added another edge to Nola’s game. But I’m hesitant to say that it alone explains Nola’s updated changeup. Simply throwing the pitch more often, approaching it like a primary rather than secondary pitch, may have helped his command. 

There’s also the mystery of his sinker, which in 2020 did not receive the benefits of a better pitch design. In terms of its pitiful whiff rate (3.6%) or relatively high wOBA (.330), the pitch was the worst aspect of Nola’s arsenal. And honestly, I’m sure what to make of it. Getting rid of it might sound like the best option, but then again, I don’t see a need for Nola to add a slider or cutter at this point in his career. In addition, the pitch’s rise to prominence is what allowed Nola to cut down on those problematic four-seamer and curves. So like most other things, it’ll take another full season of pitching for us to make a proper judgement. 

Despite the behind-the-scenes overhaul, Nola finished just 7th in Cy Young voting. This is hardly his fault, however. To show why, I first whipped up a table showing how his numbers have fluctuated over the past 3 years. There are mostly positive changes, but also one upward trend that sticks out like a sore thumb: 

Strikeout rate is up, walk rate and FIP are back down, but that HR/FB rate? Ouch. 19.6% is a rate attached to someone like Matthew Boyd, not Aaron Nola. What went wrong? 

Thankfully, not much. While many of Nola’s fly balls left the yard, just 4.8% of his batted balls were classified as barrels. That’s the 8th-lowest among 40 qualified pitchers this year. To elaborate on this point, here’s a sample of those qualified pitchers who had allowed a Barrel% of 5% or less with their HR/FB rates displayed: 

Yep, among the excellent contact-suppressors listed here, Nola is a clear outlier. He was murdered by HR/FB this year without having committed a crime. An innocent person like Nola deserves justice, but the sprint season meant limited time for a correction to occur. The spotlight went to Yu Darvish and Trevor Bauer instead, two fellow NL aces who gave up fewer home runs despite allowing a higher rate of barreled balls. If there’s any reason to doubt the legitimacy of personal accolades in 2020, well, here’s one. 

We’ve gone through Nola’s shortcomings in 2019, how he addressed them in 2020, and why he could have achieved even greater heights. Putting all of these aspects together, there’s a good case for Aaron Nola sustaining a low-3 ERA into 2021. 

There’s also the possibility that, in the long run, none of these changes will remain relevant. Such is the nature of baseball. But I don’t dedicate thousands of words to players unless I have a good amount of conviction. If all goes right, don’t be surprised if Nola unleashes a legendary season. 

Follow P365 MLB and KBO Analyst Justin Choi on Twitter! @justinochoi

Follow us on Twitter! @Prospects365

All statistics from Baseball Savant, Brooks Baseball, and FanGraphs

Featured image courtesy of the respective photographer and Getty Images

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