NEW YORK -- Brett Baty’s promising Major League career has hit an early snag.

An MRI taken Wednesday revealed that the third baseman has suffered a torn UCL in his right thumb. He will undergo surgery Thursday, which will likely cost him the rest of the regular season. A typical timeframe for such an injury requires a five-week recovery, though for now, the Mets are holding out hope for a return.

“Talking to the doctors and getting arms around it … there is a possibility that he would make it back,” manager Buck Showalter said. “The return on this is at a pretty high rate.”

The news is nonetheless a significant blow to Baty, the Mets’ second-ranked prospect who made his Major League debut Aug. 17 and homered on his first career swing. Baty had been operating as one half of a third-base platoon with Eduardo Escobar, who now figures to return to his starting role at the position.

The Mets recalled an outfielder, Terrance Gore, to replace Baty on the roster, and they don’t currently have any healthy bench players with experience at third base. As such, they plan to make another roster move before Thursday’s game, with rosters expanding on Sept. 1.

Baty injured himself diving in pursuit of a Charlie Blackmon single in the eighth inning of Sunday’s loss to the Rockies. At first, the Mets considered the injury minor enough for Showalter to consider pinch-running Baty in Tuesday’s game. But an MRI taken the following morning revealed the tear.

In 11 games with the big club, Baty slashed .184/.244/.342 with two home runs and two defensive errors. He remains a potential option for the Mets in the postseason, but it’s possible the club would hesitate to include him on a playoff roster given his overall lack of experience and playing time down the stretch.

Another left-handed-hitting third baseman, Luis Guillorme, is recovering from a groin strain and is due to begin a Minor League rehab assignment on Sunday. He’ll eventually be an option to soak up Baty’s reps at third base, but not for at least another week or so. The Mets have so far resisted calling up right-handed-hitting third-base prospect Mark Vientos, who is slashing .283/.361/.531 at Triple-A Syracuse, and a source indicated that’s unlikely to change this week. The Mets want a more defensive-minded option at third, making Deven Marrero a more likely option.

“We’re hoping he finishes up strong down there and completes a pretty good season,” Showalter said of Vientos.

Gore, 31, last appeared in the Majors in 2020 with the Dodgers. Known primarily for his speed, the veteran has 40 stolen bases in 102 career games and could be a roster option for the Mets in October.