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The Mets’ unusual rotation benefited from a surprising youth movement last season, and not just because Nolan MacLean looked like an ace and Christian Scott impressed after returning from Tommy John surgery.
Rookie left-hander Zac Thornton emerged as a rotation mainstay despite not receiving an invite to big league camp in Spring Training. The 24-year-old has posted a 3.42 ERA in 15 starts since debuting as the club’s No. 13 prospect in mid-May.
Thornton isn’t your modern power pitcher blowing hitters with high-octane heat. His average fastball velocity of 92.3 mph ranks in the 18th percentile of MLB. Thornton recorded just 63 strikeouts in 84 1/3 innings last season with a swing-and-miss rate (17.8%), the eighth-lowest among 178 pitchers to throw at least 80 strikeouts.
How can a pitcher like that succeed in today’s game — and as a rookie, no less?
“He gives them different looks every time,” Thornton told MLB.com in August. “These guys are the best hitters in the world, so I have to keep them balanced.”
A diverse seven-pitch arsenal helps Thornton do just that. Let’s take a closer look at a few of Thornton’s critical takeaways — the one area he leans on the most, wants to improve, and is taking a big step forward.
It feels like everyone is throwing a cutter these days. Last season, 192 different pitchers threw at least 100 cutters, compared to 140 pitchers in 2021, just five years ago. Pitchers throw several fastball shapes to make life difficult for hitters, and the cutter is the perfect compliment, a hard offering designed to get into the hands of a corpse and make weak contact.
But few pitchers use the cutter as their primary weapon. Thornton is. Last season, he threw his cutter 32% of the time, the fourth-highest usage rate by a starting pitcher.
Highest cutting use, SP, 2026
Min. 1,000 pitches thrown
While most pitchers rely on a four-seam fastball or sinker, Thornton turns to his cutter with confidence against both right-handed hitters (32%) and left-handed batters (31%). It’s something he’s done since college, and the Mets have tapped into what makes him unique.
“Our pitching and development guys let me run with the cutter,” Thornton said. “I always had the pitch, so they let me have the freedom to throw it in and out of the zone. They told me to throw it. They say it’s a great pitch, it works well and hitters are off balance.”
Look at the motion scheme of Thornton’s pitches and you’ll see a lot of overlap between his cutter and slider.
Well, what’s the difference? Why are these two different pitches?
Speed is one reason. Its cutter is an average of four ticks harder than its slider. Since sliders are slower, they tend to drop more — Thornton told us that anything close to zero Induced Vertical Break is a slider.
“Intentions are also different,” Thornton said. “Drivers will be at the plate, below the zone. Cutters will be up.”
We can see this quite clearly in the heatmaps below.
Thornton releases the baseball with an upper arm angle (50°) and most of his pitches have outside vertical movement due to the high slot.
The sweeper is an exception. He breaks 12.8 inches to Thorton’s glove side, which isn’t remarkable, but in the context of Thorton’s arsenal, it’s something different. Likewise, at 80 miles per hour, Thornton is significantly slower than the other five pitches he throws at least 5% of the time.
Here’s the point: the sweeper gives hitters a completely different look.
“It’s served me really well this year,” Thornton said. “It’s a great tool for lefties, just to get them out of 85-92 [mph] range. It gave me some freedom.”
Opponents hit .200 with a 24.7% swing-and-miss rate against Thornton’s sweeper last season. Those were Thornton’s best numbers of any individual field in 2026.
Of the seven individual pitches, this is the one Thornton hopes to make the most progress in 2027.
“Everybody has told me my whole life that a good left-handed pitcher always has a changeup,” Thornton said. “I’ve always worked on it. It’s not metrically bad, but I haven’t done as many reps as I did with the cutter and everything.”
Thornton’s arm socket dictates the type of motion profile he achieves on his switch. It also does not tone or fade with arm-to-side movement; not a very inspiring pitch in itself.
But much of a changeup’s success depends on its connection to the four-seam or two-seam fastball. External modifications can work; Just ask Dylan Cease, who finally perfected the “riding” changeup that confounds hitters as he bowls with the same arm speed as his four-seamer despite a large velo differential. Some other comparable lefties like Patrick Sandoval and Noah Cameron excel with changeups that have unique motion profiles.
Thornton just needs to make that connection between his changeup and his fastball. In a small sample size — Thornton threw just 58 changeups last season — batters went 6-for-17 with a 10.3% swing-and-miss rate against the pitch.