Nolan McLean Is Right On Schedule As Mets' Ace of the Future

[N.B. Lindberg]

Image courtesy of © Brad Penner-Imagn Images

The New York Mets’ season, to say the least, has not gone according to plan. They enter the second half a 40-57 team, good enough for a 1.5-game lead over the Colorado Rockies for the worst record in the National League. The majority of their offseason moves have flopped, and they’ve been just as hapless under Andy Green as they were under the Carlos Mendoza line. The only positive things you can say about this team are that Juan Soto continues to be a Swiss-made hitting machine and Nolan McLean looks the part of a frontline starter. 

Debuting late in 2025, McLean’s eight-start cameo shot expectations into the stratosphere. It’s impossible not to get excited when a touted rookie pitches to a 2.06 ERA, 30.3% K%, 8.5% BB%, and 61.1% ground ball percentage. Despite his ace-level production, the Mets famously faltered down the stretch, but heading into 2026, nearly every media outlet was bought all the way in on McLean. 

McLean was FanGraphs’ number one pitching prospect, third overall with a 65 grade; Baseball America ranked him as 2026’s top rookie in a class they mused could be historic, and ESPN ranked him as the 100th best player in the MLB. As Michael Jordan would say, “the ceiling is the roof.” So, now that McLean has 107.1 innings under his belt in 2026, we can see just how well he has lived up to the hype. 

Let’s start with the obvious. McLean’s 2026 ERA of 3.52 is nowhere near his incandescent debut. However, if you were expecting him to replicate a 2.06 ERA, or even exceed it, I’ve got some bad news for you. Since 1946, the post-war period, the lowest career ERA for anyone who has thrown over 500 innings is Mariano Rivera’s 2.21 mark. As I’m sure you’re aware, Rivera was a single-inning reliever, and the best to ever do it. Among pitchers who were nominally starters, the lowest career ERA of the post-war period is Clayton Kershaw’s 2.53, with only 14 starters owning a career ERA below 3.00. 

Not to be that guy, but if you thought McLean was going to run sub-2.50 ERAs for the next 1,000 innings, congratulations, you played yourself. Eventually, regression comes for everyone. Paul Skenes posted a 1.97 ERA over his first 320.2 innings and is currently sporting a 3.57 ERA 108.1 innings into 2026. Fortunately, it’s the 21st century, so we have far better tools to analyze pitcher performance than just earned run average. 

McLean’s debut was legitimately exceptional, but all of his ERA estimators thought he was running quite hot. His xERA, based on Statcast data, was 3.56, his FIP was 2.97, and his xFIP was 2.78. In any given season, those are still elite, top-of-the-rotation figures, but they’re usually not going to win you the Cy Young without some help from BABIP (batting average on balls in play) and home run luck. When you stack his ERA estimators from 2025 and 2026 next to each other, McLean’s supposed step back looks far less pronounced.

What’s interesting is that BABIP isn’t the culprit here. His 2026 BABIP of .272 is actually better than his .275 in 2025. The main change for McLean has been his inability to strand runners. In 2025, his left-on-base percentage (LOB%) was 84.1%, but that figure has dropped massively to 68.9% in 2026. Generally, better pitchers have better LOB%, but among starters in the post-war period with over 500 innings pitched, Andrew Abbot is the only player with a career LOB% over 80% (80.6%), and the lowest is Luke Hochevar at 63% (and his career 5.44 ERA). 

McLean was never going to continue to strand runners at an 84% clip, and he won’t continue to post a sub-70% figure going forward. The league average LOB% has been around 72.2% the past two seasons, and it’s very likely he’ll settle in around a 73% to 77% LOB% going forward, which will have the added benefit of shaving his ERA down a tad. 

While it might not feel like it, McLean’s underlying pitching ability hasn’t changed much between 2025 and 2026, even if the results have. However, that doesn’t mean he hasn’t changed as a pitcher. 

The most notable change in his underlying performance has been the complete erosion of his groundball percentage. MLB teams have moved away from trying to build groundball-generating machines, but that’s not because groundballs aren’t valuable; it’s because strikeouts are simply the best, and the two are mostly mutually exclusive — unless you were Nolan McLean in 2025. 

To put it mildly, McLean’s combination of strikeout and groundball rate in 2025 was absurd. He combined a 30.3% K% and a 61.1% groundball rate, which, if held over a full season, would have been historic. Since 2000, the highest single-season starting pitcher groundball rate was Derek Lowe’s 67% mark in 2006 and 2002, which he paired with sub-15% K%. In fact, there have only been 37 qualified seasons where a starting pitcher has posted a 60% or better groundball rate, and among that group, the highest (non-2020 division) K% was Tyson Ross’s 25.8% mark in 2015. 

While it would have been fair to assume that McLean’s strikeout and groundball rates would regress a bit, armed with a nasty sinker and the bendiest of breakers, there was no reason to believe that he couldn’t continue to be a strikeout-groundball-generating unicorn. Unfortunately, his groundballs have all but evaporated in 2026, and his pairing of a 27.9% strikeout rate and 47.8% groundball rate looks far more ordinary (although still excellent in a vacuum). 

Digging into the granular data, McLean has seen his groundball rate drop on nearly every single one of his pitches, and that drop has been most pronounced on his pitches with arm-side movement. Last season, he posted groundball rates of 79.5%, 63.2%, and 44.4% on his sinker, changeup, and fourseam fastball, but has seen those figures move to 54.4%, 47.4%, and 26.8% in 2026. 

The scale of this shift is staggering, and there are a few things at play pushing McLean’s groundball rate up and off the ground. The first is his arm angle. In 2026, McLean’s average arm angle has increased to 31 degrees from 27 degrees in 2025. But that vertical tilt up has not been uniformly distributed. 

On almost every pitch, McLean has bumped his arm angle up by about three degrees, but on his sinker it has shot up by five.

There’s nothing magical about arm angles, but they do impact pitch characteristics and can have a downstream effect on pitch location. Unsurprisingly, all of McLean’s pitches have seen their movement characteristics change, but none more so than his sinker. 

*Horiztonal and Vertical Movement is relative to the league average per pitch

McLean went from throwing a sinker with extreme vertical movement (drop) and comparatively minimal horizontal movement, to one with substantially more horizontal movement, but far less drop. The pitch’s effectiveness hasn’t waned, but it has altered its strengths. It went from generating gobs of ground balls but getting hit hard (92.4 MPH average exit velocity) to being an elite contact suppressor (86.8 MPH average exit velocity). On top of getting more on top of the ball, McLean’s new release point seems to have shifted where he is able to locate consistently. 

The difference might appear subtle, but in 2025, McLean was much more consistently locating his pitches lower in the zone. Once again, this isn’t a good or bad thing, but it marks a notable shift. Pitches lower in the zone will generally generate more ground balls, while certain pitches at the top lead to more whiffs and weak aerial contact. 

We’re a little more than halfway through McLean’s rookie season, and he has already established himself as one of the brightest young starters in the league. His breaking balls have elite movement characteristics, and he has a deep arsenal. However, where he goes next will be fascinating to see. 

There are real changes under the hood for McLean this season that have made him a slightly different pitcher, but not necessarily a better one. Before jumping to conclusions on whether the Mets need to bring back the old McLean, he deserves a period of grace to work with his new arm angle. 

Throughout the minors, McLean, a former two-way college player, always had elevated walk rates. It’s not that he has awful control, but he’s so new to pitching, and his pitches move so much, that he’s likely nowhere near his command potential. When you factor in the new arm angle and new pitch characteristics that follow, it’s no surprise he has taken a slight step back from that dominant 2025 run. 

To make it clear: The kid is right on schedule, just not ahead. He’s made changes at the big-league level and still found success, and there’s tons of untapped potential. It wouldn’t surprise me if he finds his pitches again and rips off a dominant ten-start run to close the season. The Mets have their ace of the future, even if the ERA doesn’t say it yet.

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