Aaron Nola’s Velo: Should the Phillies Worry?

Entering his final season before free agency, the Phillies and Aaron Nola worked diligently to come to an agreement on a contract extension prior to Opening Day. Though it did not come to fruition, it did not change the fact that Nola would be relied on to log another 200 innings for the defending National League champs and receive Cy Young consideration––like he had in 2022, where he finished fourth in voting. A bumpy start to the season, though, may have lowered expectations.

In six games this year, the Phils’ righty has pitched to a 4.66 ERA in 36.1 innings and has been susceptible to the big inning for opposing offenses. It’s a small sample size––having only thrown 17.6% of the innings he threw last regular season––but Nola is striking out just 19.3% of batters faced. To put that number into perspective, it is about 8.1 percentage points below his career average.

Nevertheless, Nola’s past two outings have been encouraging signs that he has turned the corner. After allowing a first inning three-run home run against the Rockies on April 21, Nola rebounded to throw seven strong innings en route to a Phillies 4-3 victory. Then, on April 28 in Houston, the ace stymied the Astros’ offense over eight innings––a season high leading the Phillies to victory. 

Though it looks like the Louisiana native may have found his groove, his fastball velocity is showing signs of decline––especially in the middle innings. As detailed in Matt Gelb’s recent article in The Athletic, Nola’s average fastball velocity in innings 4-6 this season has fallen to 90.8 mph––down from 91.6 mph in 2022 and 91.8 mph in 2021. 

Now, Nola has never been the hardest thrower––this season, he ranks in just the 12th percentile among qualified pitchers in fastball velocity. The righty relies on a five pitch mix that includes a high spin knuckle-curve, cutter, sinker, and changeup with each pitch having more break than league average. This has allowed Nola to keep the ball off the barrel of the bat, inducing soft contact while generating swings and misses. For the type of pitcher that Nola is––especially one that commands the zone extraordinarily well––a diminishing fastball may be meaningless. However, considering it is his contract year and the league-wide expectation that he will obtain a contract near $200 million in total value, it is of some concern.

There are numerous factors that could be contributing to a decline in velocity. For one, the pitch clock. Without time to catch your breath on the mound during innings, it would not be surprising if Nola is tiring faster than he has in previous years. The same can be said for limitations on pickoffs. Stepping off the mound or lobbing a ball over to first was a common occurrence for Nola over his career to settle himself with men on base. Now, with pitchers only allowed two disengagements, he may feel rushed on the mound without a clear way to slow the game down and execute his pitches. It’s something he’ll need to adjust to.

The other factor that could be at play is the mileage on his arm. Though Nola is just 29––he turns 30 on June 4––he has thrown at least 180 innings the last four full seasons, eclipsing 200 innings in three of them. Over his career, Nola has thrown 1264.2 innings in the regular season and has now thrown deep into October. 

It’s not unusual for a pitcher’s fastball to start slowing down after logging that many innings.

Take Madison Bumgarner, for example. The now 33-year-old was a catalyst during the San Francisco Giants’ even year magic run in the early 2010s. For about a six year stretch, he was regarded as one of the best pitchers in baseball, and perhaps the best postseason pitcher. However, after logging 1397.2 innings, his peripheral numbers began to decline from 2017 onwards. During that time, he was still an effective pitcher, but he began walking more and striking out less as he saw his ERA and FIP climb. The lefty also saw his average fastball velocity decline significantly from a high of 92.7 mph in 2015 to 89.6 mph in 2018 and 87.2 mph in 2023.

Bumgarner was DFA’d by the Diamondbacks on April 20.

This is not to say Nola is on track to be the next Bumgarner––the lefty’s numbers really took a hit following his 2019 season after he had logged 1846 regular season innings. Nola is far from that mark and is the type of pitcher that can still be effective as his arm continues to add mileage. However, when considering the possibility of awarding him a long-term, expensive contract, the Phillies should be wary of the potential for their ace to slow down in the final years of the deal. 

Nevertheless, a slightly diminished fastball will not substantially affect Nola’s 2023 season. As he continues to become more comfortable with the pitch clock, the Phils’ ace will find his groove and, hopefully, pitch deep into October again. 

Photo: Miles Kennedy/Phillies Team Photographer