Yet again, the Mets are looking to their farm system for a spark and help at the Major League level. Only this time, it’s to fill innings. Zach Thornton, who’s pitched very well since 2026 Spring Training, will make his MLB debut on May 20 against the Washington Nationals. It comes after a higher swing-and-miss rate in Double-A, and low walk numbers that’ve become the standard for the lefty.
A Look at Thornton
The Mets made Zach Thornton a fifth-round pick in 2023 out of Grand Canyon, part of an MLB Draft that is looking for the organization. As we noted earlier in May, that draft also netted the team Brandon Sproat, A.J. Ewing, and Nolan McLean.
During his junior season at GCU, where he played alongside current A’s shortstop Jacob Wilson and current Minor League prospects Homer Bush Jr. and Isaac Lyon, Thornton gave up 14 home runs. However, he struck out 91 over 88 innings with the Lopes.
Thornton’s numbers in A-ball weren’t loud in 2024, his pro debut season. The lefty didn’t walk a lot of hitters, nor did he give up a lot of home runs, but only struck out 54 over 68 innings. However, he took a big step forward in 2025, as Thornton posted a sub-1.00 ERA in High-A before he moved to Binghamton.
In Double-A, Thornton didn’t have a high swing-and-miss rate (26.3%) but struck out 53 over 52, only allowed 36 hits, and nine walks allowed with the Rumble Ponies. But that swing-and-miss ticked up in 2026, as Thornton posted a Whiff% of 30.9% in Double-A Binghamton in April. He made just one more start at the level before he moved to Triple-A.
Thornton struck out 13 over 12 innings with Triple-A Syracuse before the move.
The 24-year-old isn’t a hard thrower by any means, as Thornton topped out at 94 MPH in Triple-A and has mostly sat in the low-90s. However, there is deception with the delivery & the fastball does have some ride and cutting action to it. But his fastball helps set up what is a very good slider, one with runaway action on left-handed hitters.
That slider was his most-used pitch at the Triple-A level, so much so that it saw roughly 40% usage in his final start in the Minors before his promotion. It’s a good pitch and one that didn’t get hit well during his brief stint with Syracuse. While the pitch had just a 29% Whiff%, just two of the 61 times it was thrown resulted in a hit.
The Mets will have to add Zach Thornton to the 40-man roster before his call-up.
Analysis
The Mets are in a tight spot in terms of pitching depth.
Kodai Senga is on the IL thanks to a back injury, while Clay Holmes suffered a fractured fibula in mid-May against the Yankees. The loss of Holmes was a significant one, given that he pitched so well and was, arguably, the Mets’ best starter before he went down.
He also jumped two other notable pitching prospects in Triple-A, Jonah Tong & Jack Wenninger.
Wenniger walked 22 over 35.2 IP this season for Syracuse, even though he owned a sub-2.00 ERA. Tong, who is on the 40-man roster, is second in the International League in strikeouts with 55. However, he didn’t pitch well in Spring Training, and walked 24 over 38 with Syracuse.
Thornton, meanwhile, did pitch well in spring with a 1.35 ERA in Grapefruit League action.
It’s an aggressive assignment, to say the least. However, Thornton does throw strikes, has a full arsenal to work with, and as noted earlier, can be deceptive.
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