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Breaking Down Offseason Targets - Aaron Nola

The presumptive top American arm on the market is a true workhorse who saw his numbers decline in 2023.

Division Series - Atlanta Braves v Philadelphia Phillies - Game Three Photo by Rich Schultz/Getty Images

Now it’s time for a breakdown of the last of the big 3 domestic free agent pitchers, and the one who will probably command the largest contract - Aaron Nola. I covered Blake Snell here and Sonny Gray here so feel free to go back and read those articles if you’re interested in my breakdown of those arms.

Between the 3 aforementioned pitchers, I think Aaron Nola is the most interesting free agent to consider. He’s been one of the top pitchers in the league for a while now but actually had less fWAR than both Blake Snell and Sonny Gray this year.

Does that mean he’s not worth his price tag? Is he likely to get overpaid? Is he actually the top domestic free agent arm on the market this year?

These are all questions that I want to consider so let’s get started.


As I’ve done with every other pitcher in this series so far, I want to provide the Fangraphs page of the guy we’re considering.

One thing immediately jumps out at me and that’s Nola’s durability. I mean, I don’t think the guy has missed a start in 6 years. That’s incredible for anyone but especially for a pitcher. We’ve already looked at Blake Snell, who has missed starts for a variety of reasons over the years and has only made more than 30 starts in a season twice in his career, but that’s not Aaron Nola. The right-hander is as durable as it gets for a pitcher and that’s a serious mark in favor of signing him.

The second thing that I notice is a serious aversion to walks. In the last 3 seasons, Nola has posted walk rates of 5.2%, 3.6%, and 5.7%, respectively. For reference, the league average this year was 8.6%. Nola has finished with a walk rate above that just one time in his career (2019) and he finished with “only” 3.4 fWAR that year, the lowest total he’s ever posted in a full season.

And that fact right there emphasizes just how good Aaron Nola has been. His worst full season was still better by fWAR than the 2023 season of Miles Mikolas, the Cardinals incumbent “ace”. So, make no mistake, signing Aaron Nola not only improves the rotation but it does so significantly.

There’s also the fact that Nola’s expected stats were significantly better than his actual stats. It gets better, though. Nola was worth 3.9 fWAR this year and Sonny Gray was worth 5.1. That’s a large difference but were the two pitchers really all that different?

The answer is no. Sonny Gray’s expected ERA this year was 3.69. Nola’s was 3.77. Gray’s xFIP was 3.65 and Nola’s was 3.63. The two pitchers were remarkably similar this year but home run luck played a significant role in separating the two. Considering that and then the ages of the two pitchers, I would expect Nola to have more good years left than Gray and I wouldn’t even be all that shocked to see him eclipse 4 WAR at least once or twice more in his career.

So, yes, in my mind, Nola is the American arm on the market this year.

With that said, Nola’s strikeout rate declined this year and he finished with his lowest strikeout rate since 2016. That’s a legitimate concern that is worth investigating. Will his strikeout rate rebound or is this what he is going forward?

Let’s take a look under the hood and see if we can answer that question.

Pitch Level Data

Something that might help us answer that question is stuff+. Taking a look at Nola’s stuff+ last year and comparing it to this year tells us that his stuff did indeed get worse.

Aaron Nola Stuff+ Changes

Pitch 2022 Grade 2023 Grade
Pitch 2022 Grade 2023 Grade
Four-Seam Fastball 106 95
Curveball 129 118
Sinker 105 100
Changeup 69 70
Cutter 107 111

So stuff+ tells us that Nola’s 3 main pitches got worse this year. That can help explain the dip in strikeout rate. But let’s not take stuff+’s word for it; let’s verify!

We’ll start with results. If Nola’s four-seamer is indeed worse, the we should expect it to play worse. And that’s exactly what it did. Last year, the pitch allowed a .269 wOBA while getting whiffs at a 24.2% rate. This year, the pitch allowed a .338 wOBA while getting whiffs at a 21.8% rate.

While that might seem like a big change, I want to point out two things. The first is that the run environment of the league changed with the league ERA rising from 3.97 to 4.33. The second is that Nola’s fastball was worse in 2021 (.344 wOBA, 22.4% whiff rate) and had a stuff+ of 103 that year. So, is Nola’s fastball truly worse or is this just year over year variance?

Let’s take a look at his pitch metrics to help answer that question.

His velocity was basically unchanged, dropping just 0.1 mph, and so was his spin, so that’s not the cause. The change here appears to be in the movement profile as Nola’s four-seamer lost 0.3 inches of induced vertical break and 0.9 inches of run.

Honestly, that’s not too concerning to me. A dip in velocity or a bigger loss in movement would raise more red flags. Such a slight change in movement profile with no apparent cause other than a slightly higher release point, makes me think this could easily just be normal year over year variance. It’s something to keep an eye on for sure, but I’m not overly concerned about it.

In fact, when I look at the pitch data for Nola’s sinker, I come to the same conclusion. The only pitch that really had an appreciable difference was his curveball, which gained nearly a full mph of velocity and lost about an inch of drop and 2 inches of sweep. Stuff+ seems to think that’s not a worthy trade off, but that makes sense because the pitch did add some gyro spin too, which limited its movement profile.

That’s a minor, but legitimate, change that may have led to Nola’s curveball playing a bit worse this year and not missing as many bats.

There’s probably another factor at play here too, at least when it comes to the curveball.

In 2023, Aaron Nola made his curveball his primary pitch, bumping up its usage from 26.5% to 31.3%. It’s reasonable to think that increased usage would lead to a slight dip in the performance of the pitch as it loses some element of surprise.

Of course, an increase in the usage of one pitch must necessarily lead to a decreased usage of the others, and the pitch that saw the biggest downturn was Nola’s four-seamer.

The bigger story here, though, is that this isn’t just a one year trend.

In 2021, the righty threw his four-seamer 37.5% of the time. That figure dropped to 33.4% in 2022 and then dipped even further to 29.4% this year. Nola is making a clear effort to de-emphasize his four-seam fastball, though he is throwing more sinkers.

In total, Nola finished the year with a fastball usage below 50% (48.3%), and while I’m generally on the “throw fewer fastballs” bandwagon, I do want to see Nola’s curveball rebound. That’s going to be the big weapon for him, especially if it’s going to be his primary pitch moving forward, as he tries to prove that he has better years ahead of him.

Now, I don’t mean to say that as if Aaron Nola is a bad pitcher. A 3.9 fWAR pitcher is certainly not bad but there’s a big difference between paying for a 3-something fWAR pitcher and a 4-5+ fWAR pitcher.

The question of whether Nola is worth the contract that he will command this winter is basically a question of whether or not he can get himself back in the 4-5+ fWAR range.

If things has broken differently for Nola, he could very easily have been in that range this year. Some poor home run luck meant that Nola’s 4.03 FIP was a good bit higher than his 3.63 xFIP. That little fact makes his 3.9 fWAR season look a little more impressive.

I’ll also say that I’m not completely sold on the idea that his stuff is worse. His curveball might actually be a little worse if he can’t remove the extra gyro spin that he added this year but his fastball “decline” looks more like year over year variance to me at this point.

With that said, not everything has an easy answer and I could easily be wrong about that. I would say check back with me in a year on that but Nola is a free agent now so that’s not really helpful. Suffice it to say that I’m not scared off by the decrease in strikeouts nor the decline in fastball stuff+ but those are things to be aware of.

The current version of Aaron Nola is pretty darn good, though, and there is value in never missing a start.


I’ve now broken down each of the top 3 domestic options on the market so I want to end by wrapping all my thoughts together here. First, though, there’s one interesting stat that I want to mention.

These 3 arms were remarkably similar in 2023 so the challenge facing the Cardinals is determining who will be better going forward, and how much each pitcher is worth over the life of their next contract.

Blake Snell, as I mentioned in the article on him, has the best stuff of the three major domestic free agent pitchers. There are a lot of questions with him, though. For instance, how many innings will he pitch in a season? He cleared 180 this year but that’s only the second time he’s even cleared 130 innings pitched in a season. And then there’s his increased walk rate. Is his increased walk rate, and specifically, his decline in fastball command, a sign of things to come?

The arm talent is real with Snell but I would stay away. There are just too many risks, on top of the ever-present risks of being a pitcher, to make me feel comfortable about signing Snell to a long-term deal after the age of 30.

For Sonny Gray, there are some similar questions about how many innings he will throw in a year. He was healthy in 2019 and 2020 but then threw just 135 innings in 2021 and 119 innings in 2022. He did make all 32 starts this year but some recent durability concerns with a soon-to-be 34-year-old who just jacked up his sweeper velocity is something to be aware of. Beyond that, though, Gray has been remarkably consistent for the last 5 years and has been a good pitcher for a long time.

Combine that with the fact that he’ll likely get the least money and shortest contract of the 3 and I’m in on Sonny Gray. With that being said, I do have a caveat - he shouldn’t be the best arm the Cardinals acquire. So if the Cardinals want to sign a good number two arm (who should be around 3 fWAR next year) while minimizing the risk incurred by signing a higher end pitcher, I’m all for it.

And that brings us to Aaron Nola. I consider Nola to be a higher end Sonny Gray. Both have been consistently good, both limit their walks, and both aren’t huge strikeout arms. The difference is that Nola is an iron man and has a better shot at getting into the 4-5 fWAR range again. He’s also about 3 and a half years younger. That matters when we’re talking about big money and long contracts.

I would much prefer Nola to Snell, though that preference depends on contract size, but I still prefer Gray to Nola, again depending on what the final contracts shake out to be.

Since I would prefer to only surrender one draft pick and not too, I’ll limit my choice to just Sonny Gray.

But remember, I said that Sonny Gray shouldn’t be the best pitcher the St. Louis Cardinals bring in, so it’s a good thing there are more pitchers on the market. I’ll continue my breakdown of the top free agent options next week and take a look at the Japanese arms that have me interested.

Thanks for reading, VEB. Have a great Tuesday.