Aaron Nola’s Stellar Start

With the Phillies officially one-third of the way through this abbreviated season, their horse at the top of the rotation appears to be having a career year and pitching at a level reserved for the very best aces in the sport. After four starts Aaron Nola has a 2.05 ERA, a career high 12.6 K/9 and he’s reminding fans of his Cy Young-caliber 2018 season. What is driving the Phillies No. 1 to these new heights?

When most people think of Aaron Nola, the first thing that comes to mind is his disgusting curveball. I mean, just look at this thing render 2019’s home run leader completely helpless:

Anyone that sees a pitch like that would want him to throw it as often as possible and that’s exactly what the strategy was in 2019: he threw it as much as his fastball, opting for the curve with more than a third of his total pitches. He had mixed results leaning so heavily on the pitch, as his 2019 was something of a mixed bag with stretches of ace-level pitching often followed by a string of poor starts in which he struggled with opposing lineups the third time through the order.

It’s been a different story in 2020. Nola has been completely dominant, setting down the dangerous lineups of the Yankees, Braves, and Mets in his last 3 starts and holding each of them to 3 or fewer hits in 7+ innings. Something has clearly clicked for him that wasn’t there last season.

That something appears to be a drastically increased reliance on his changeup. In 2019 he used it 18.9% of the time, a distant third behind his 4-seam and curve, both of which he threw over 35% of the time. Enter Bryan Price as pitching coach, a man with a reputation for encouraging his pitchers to throw changeups. Now Nola is throwing that pitch at a 31.7% clip, which makes it his most-used pitch so far.

How good has that changeup been? According to fangraphs’ Pitch Values, it’s been the 5^th-best changepiece in the league among qualified pitchers. When batters swing at the change they miss it nearly half the time, whiffing at a 47.5% rate.  The pitch is so effective because its tailing movement is almost identical to his 4-seam fastball’s, except it comes in 7-10 mph slower and falls off the table in the strike zone:

	Horizontal Movement	Vertical Movement	Velocity
4-seam Fastball	14 inches of break	20.2 inches of drop	92.3
Changeup	14.2 inches of break	35.2 inches of drop	85.1

This deception has benefited both pitches; his fastball has been the 13^th-best in the league among qualified pitchers by that same Pitch Values statistic, a dramatic improvement from last season when it ranked 54^th.  Hitters last year had a .376 WOBA against his 4-seam, which means they hit like Josh Donaldson or DJ LeMahieu against it. This year that number has plummeted to a microscopic .054, which is roughly equivalent to how AL pitchers hit when they visited NL parks last year.

Nola has also noticeably changed his approach against left-handed hitters, substituting his changeup for his curveball as his favored secondary offering. Last year the 4-seam and curve made up 67% of his pitches against southpaws; this year the 4-seam and change are being thrown 70% of the time in those plate appearances. He’s essentially swapped the change and curve in usage, now only breaking out the hook to get strikeouts, and it’s working: he’s holding left-handed batters to a .263 OPS in 2020, a clear improvement from 2019’s .727 OPS. And when he can do this with it, who can blame him:

Interestingly, throwing the curve less has made his premium pitch even more devastating, perhaps because hitters are seeing it less than before and consequently are not prepared for it. It has become a truly elite out pitch: a 41.6% whiff rate and a staggering 57.6% putaway rate, meaning when Nola throws the curve in a 2-strike count he gets the K well over half the time. When it comes to his curve, less appears to be more.

Put it all together and you have a pitcher with improved command (he’s walking batters at a career-low 1.37 per 9 clip), 3 elite pitches, and a better plan for attacking hitters and going deeper into games by keeping hitters off balance with a less predictable approach. 2018 Nola was special, as evidenced by the 3^rd place finish in Cy Young voting, but the pitcher we’re seeing in 2020 might be even better.