Phillies: What’s Up With Aaron Nola?

ATLANTA, GA JULY 02: Philadelphia Phillies starting pitcher Aaron Nola (27) looks out from the dugout after pitching 8 scoreless innings during the game between the Atlanta Braves and the Philadelphia Phillies on July 2nd, 2019 at SunTrust Park in Atlanta, GA. (Photo by Rich von Biberstein/Icon Sportswire via Getty Images)
ATLANTA, GA JULY 02: Philadelphia Phillies starting pitcher Aaron Nola (27) looks out from the dugout after pitching 8 scoreless innings during the game between the Atlanta Braves and the Philadelphia Phillies on July 2nd, 2019 at SunTrust Park in Atlanta, GA. (Photo by Rich von Biberstein/Icon Sportswire via Getty Images) /
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(Photo by Alex Trautwig/MLB Photos via Getty Images)
(Photo by Alex Trautwig/MLB Photos via Getty Images) /

Fastball Location

Aaron Nola operates with a four-pitch arsenal, utilizing a four-seamer, a sinker, a change-up, and a knuckle-curve. He owed much of his success in 2018 to keeping hitters off-balance at the plate through pitch mixing and movement, as opposed to than overpowering velocity.

That rings true this season, as his pitch-mix split and pitch velocities are virtually the same this year as they were during 2018. Seeing that pitch percentages and velocity aren’t the issue, perhaps we should take a look at the next most obvious suspect – pitch command.

Since August 25, Nola has had issues locating his fastballs, taking into account both his four-seamer and sinker. Typically, Nola makes his living by inducing whiffs and poor contact quality by locating fastballs on the outskirts of the strike zone, capitalizing on the natural run of his heater.

In his past four starts, however, these pitches have been catching far too much of the plate. Comparing Nola’s fastball heatmap before his start in Miami on August 25 to his heatmap after, we can see more fastballs have found the middle of the zone.

Hitters have taken advantage of these fastballs hovering over the middle of the plate, too. xwOBA is a metric developed by Statcast that conveys the expected weighted on-base average for a given batted ball, taking into account contact quality. In the 27 starts he made before August 25, his fastball was being hit for .342 xwOBA, according to Statcast.

Since, however, it’s been tattooed to the tune of a .412 xwOBA. As much as baseball has evolved in recent years, one surviving truth is that fastballs over the heart of the plate are easier to hit. If he’d forgotten that fact at all, Aaron Nola has surely been reminded of it in recent weeks.

If Nola can return to locating his heater on the outer parts of the plate, hitters would have a much more difficult time making solid contact with it. They also would struggle more in adjusting to off-speed offerings, which has been another culprit of the righty’s struggles.