Why Zac Thornton Shouldn't Be an Automatic for the Mets' 2027 Rotation

Zac Thornton has made a positive impression in his first stint as a big leaguer. But the Mets shouldn't automatically place him in the same category as Nolan McLean and Christian Scott with a guaranteed rotation spot in 2027.

The New York Mets will give Zac Thornton an extended audition for a rotation spot down the stretch. | IMAGN IMAGES via Reuters Connect

The 2026 season is firmly in evaluation mode for the New York Mets, who traded away players such as Freddy Peralta while also looking at some of their young players. Peralta's departure offers further runway for young lefty Zac Thornton to see if he can claim a spot in the 2027 rotation.

Thornton, who was initially lumped in with an uninspiring collection of fifth-starter options for the Mets earlier this season, has made the most of his big-league opportunities so far. Throughout his first six starts, Thornton is 2-2 with a 2.88 ERA and 1.05 WHIP, compiling a 24:10 strikeout-to-walk ratio in 34.1 innings pitched.

While there have been moments of brilliance for Thornton, such as a one-run effort against the Philadelphia Phillies in his second big league start on June 26, last Saturday's start against Miami was not one of them. Thornton struggled with his command, racking up 57 pitches in the first two innings of the game as he allowed four runs (three earned) on six hits and three walks in 4.1 innings pitched.

Why the Mets should be wary about guaranteeing a 2027 rotation spot for Zac Thornton

The surface-level numbers for Thornton look fine, but a deeper dive into Thornton's Baseball Savant page shows signs of concern beneath the surface. The biggest sign of alarm is that Thornton's expected ERA is 4.83, nearly two full runs higher than his current 2.88 mark, which could be a sign that Thornton has gotten lucky with batted balls so far in his career.

Opponents are also expected to have a higher batting average (.273 vs. .215 actual) and slugging percentage (.443 vs. 322 actual) against Thornton, which isn't shocking considering how he works. Thornton is a command-based soft-tossing lefty who relies on the ability to locate his pitches to be successful.

That kind of pitcher can be useful in a big-league rotation, as guys like Jose Quintana have made a career out of hitting their spots. The problem is that Thornton has a long way to go to showcase that he can establish himself as a premier control guy like Quintana. His current six-start sample size offers hints that Thornton is a back-of-the-rotation arm, not a true front-line option like Nolan McLean or Christian Scott.

McLean and Scott figure to be the only sure things in the 2026 rotation, with Peralta and Clay Holmes out the door. Sean Manaea and Kodai Senga are under contract as well, but Thornton's small sample size hasn't shown enough to put him above either of those pitchers, giving him an inside track on a rotation spot next season.

There is nothing wrong with having pitchers like Thornton, however, in the mix as depth options. Thornton's floor is a pitcher who can go five or six innings while allowing three runs, which is a useful arm to have in a rotation that tends to prioritize ceiling over floor. Those types of dependable innings-eaters can help a team get through the regular season, although a lack of proven stuff makes them harder to rely on in the postseason.

Given that he is still young and will have minor league options remaining, Thornton should be viewed as part of the team's depth moving forward and given an opportunity to either earn a rotation spot down the stretch or compete for one next season. Handing a job to Thornton unquestioningly is a very risky move.

However, it would be poor roster planning to assume that Thornton can fill a rotation spot on a team that needs upgrades in multiple areas to contend in 2027.