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The good, the bad, and the funny: Aaron Nola’s 2021 season

Nola’s 2021 season has been marked by the highest of highs and the lowest of lows. Let’s take a closer look.

MLB: Arizona Diamondbacks at Philadelphia Phillies Bill Streicher-USA TODAY Sports

Aaron Nola. Aaron Michael Nola. Who better to write “The Good, The Bad, and The Funny” about than a man who has clearly had his fair share of all three this year? Before we really get started, let me share this little tidbit.

Over the past five seasons, only four pitchers have qualified for the ERA title all five years while posting an ERA of 4.30 or lower: Max Scherzer, Zack Grienke, Gerrit Cole, and Aaron Nola.

Six other pitchers have done it in four of the past five seasons: Zack Wheeler, Luis Castillo, Jose Berrios, Lance Lynn, Jacob deGrom, and Yu Darvish. That’s an extremely impressive list to be a part of. Every one of those players is an All-Star. The average 2021 salary of those ten pitchers is $22.7 million.

Say what you will about Aaron Nola’s season, but he has remained healthy all year, averaged nearly 6 innings per start, and posted a respectable ERA. Sure, that’s disappointing when you’re expecting an ace. But on a $12.25 million salary? I’ll take it.

The Good

Nola’s best outing

Aaron Nola’s best start came on April 18 against the Cardinals, when he pitched a complete game shutout, striking out ten and walking none. He allowed only two hits (both singles) and the Cardinals never had a man advance into scoring position all game. By game score (93), that outing currently ranks as the ninth most dominant start of the season.

His numbers at Citizen’s Bank Park

Nola has started 12 games at home. He’s averaging 5.86 IP per start at Citizen’s Bank Park with a 3.33 ERA, a 2.56 FIP, and a 2.87 xFIP. His opponents are hitting just .219/.258/.357 (.615 OPS) in those starts. His strikeout-to-walk ratio at home is 8.55, which leads the major leagues.

Walks and strikeouts

His K/9 and BB/9 have been elite at home and still well above average on the road as well. His 5.48 K/BB ratio this season ranks third in the NL and fifth in the majors. His 10.96 K/9 is the highest he’s ever had in a full season (he had an absurd 12.11 K/9 in 2020), and his 2.00 BB/9 is the lowest of his career.

His ERA estimators

There are several statistics that attempt to estimate a player’s deserved ERA and that have proven to be effective predictors of a player’s ERA moving forward. Every single one of those statistics suggests that Aaron Nola ‘deserves’ a significantly better ERA than he’s posted so far. These stats aren’t perfect, and anyone watching knows that Nola has struggled to keep runs off the board at times this season. Nevertheless, these numbers deserve some attention, especially since they all tell such a similar story.

  • 3.39 FIP
  • 3.41 xFIP
  • 3.44 xERA
  • 3.29 SIERA

By all of these metrics, Aaron Nola has been a top-ten pitcher in the National League.

The Bad

Nola’s worst outing

Aaron Nola has had some real stinkers this year. While his 4.30 ERA and 148.2 IP suggest that he’s still been a reliable starter if not an ace, he’s had enough bad outings that I’d hesitate to describe 2021 Nola as “reliable”. There have just been too many games this season where he didn’t give the Phillies a legitimate chance to win. By my count, he’s had ten starts this year that were mediocre or worse, including what was arguably the worst start of his career. On June 19 in San Francisco, Nola lasted just 2.1 innings and allowed 6 earned runs. He only struck out one batter, while giving up 6 hits, 3 walks, and 2 home runs.

His numbers away from Citizen’s Bank Park

Nola has always had noticeable home/road splits throughout his career (the one exception being his All-Star 2018 season), but this year he’s been particularly bad on the road and his home performance hasn’t been dominant enough to cover it up.

Nola has started 14 games on the road, and in those games he has a 5.17 ERA. His 4.13 FIP and 3.89 xFIP aren’t so awful, but they’re still much higher than his numbers at Citizens Bank Park.

Ground balls, fly balls, and home runs

Aaron Nola has been allowing runs at a higher rate than usual this year, that much is certain. But why? He’s actually allowing fewer baserunners this season than he has in the past – he has a 1.10 WHIP which is slightly lower than his 1.16 career average.

Part of it could simply be chalked up to bad luck. His 69.4% LOB% this season is 5.2 ticks below his career average (74.6%). It’s surprising that his LOB% is down this year, since usually a pitcher’s LOB% goes up when his strikeout rate goes up. Regardless, Nola’s LOB% isn’t low enough to explain all the extra runs scored.

The bigger problem is that Aaron Nola is allowing too many home runs. His HR/9 is 1.27, which is the highest it’s been since his rookie season. His HR/FB is 13.5%, which is right around his career average of 14% and the league average of 13.6%. So, these extra home runs can’t be explained away as simply bad luck.

What seems to be happening is that Nola is allowing far more fly balls this year than ever before. His fly ball rate in 2021 is 40.2%, while his career average is 31.1%. Those extra fly balls are coming at the expense of ground balls – his ground ball rate is down to 39.4% compared to a career average 48.8%. His GB/FB ratio is down to 0.98; the lowest it’s ever been before is 1.68.

Having a low GB/FB ratio isn’t necessarily a bad thing (as FanGraphs explains, “there is no ideal batted ball distribution.”) There are good pitchers on either end of the spectrum. Zack Wheeler has a 1.77 GB/FB, which is almost twice as high as Aaron Nola’s, while Max Scherzer has a 0.69 GB/FB, the lowest in baseball this season. However, in Nola’s particular case, the dramatic increase in fly balls allowed seems to explain why he’s allowing so many home runs this season. And why is he allowing so many fly balls? Well, take a look at Nola’s average launch angle against over the years:

  • 2015: 9.4
  • 2016: 6.0
  • 2017: 9.0
  • 2018: 8.8
  • 2019: 9.1
  • 2020: 8.6
  • 2021: 13.9

Batters are hitting the ball high in the air against Nola far more often than they used to. As a result, Nola is allowing barrels at a higher rate than ever before (7.2%), even though his average exit velocity against has remained relatively constant.

The Funny

Depending on your temperament, you might find this humorous or you might just find it irksome. But even if you don’t find it funny ha-ha, at least you’ll find it funny strange.

The less run support, the better?

Over the past ten years, it’s been a pretty common theme that the Phillies offense doesn’t like to provide their ace pitchers with much run support. But as it turns out, sometimes the pitchers like it better that way.

This season, Aaron Nola has a 2.47 ERA in games where the Phillies scored 0-2 runs, a 5.05 ERA in games where the Phillies scored 3-5 runs, and a 5.60 ERA in games where the Phillies scored 6 or more runs. His FIP tells a pretty similar story, although it’s less extreme:

  • 0-2 runs - 2.28 FIP
  • 3-5 runs - 4.43 FIP
  • 6+ runs - 3.73 FIP

And of course, Aaron Nola has gotten plenty of run support this year. The Phillies are averaging 4.92 runs per game in Nola starts, compared to 4.5 runs per game in all other games. They’ve scored more than 6 runs in ten of Nola’s 26 starts, which ranks fifth among all starters in the National League. Personally, I can’t decide if this is a good thing or a bad thing. Should they stop scoring runs so Nola can keep his ERA low, or should they be trying to score more runs so they can win even when Nola’s ERA is high? It’s a real catch-22.