PORT ST. LUCIE, Fla. -- Already slim, Rafael Montero's chances to make the Mets decreased to zero on Thursday. The team announced that Montero has suffered a complete tear of the ulnar collateral ligament in his pitching elbow and will undergo season-ending Tommy John surgery. 
Montero will travel back to New York City on Sunday, then meet a doctor Monday to determine when and where he will undergo the procedure. Most pitchers require 12 to 18 months to recover from that operation.
"It's not great for the kid," Mets manager Mickey Callaway said. "I feel bad for him. But it's something that happens when you pitch. He's got a long road ahead of him to recover."
Entering camp as a favorite to make the Opening Day bullpen due to his lack of Minor League options, Montero struggled -- a 9.00 ERA over seven appearances and a .316 opponents' batting average -- to the extent that he became unlikely to make the team. Facing three batters in his final Grapefruit League game Tuesday against the Cardinals, Montero retired just one of them, complaining afterward of elbow pain for the first time.
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"That was really the first time he said it," Callaway said. "That's one of the unfortunate things about being in the position that he was in, is sometimes you don't say things because you're trying to make a team. Pitchers pitch through things a lot, but identifying what you can pitch through and what you can't is important. It's just a bad situation."
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A frequent traveler between Triple-A Las Vegas and the big leagues over the past four seasons, Montero has earned nine Minor League demotions during that stretch. Despite myriad chances and flashes of excellence, he has never demonstrated consistent improvement; once a higher-rated prospect than Jacob deGrom, Montero owns a 5.38 career ERA -- including a 5.87 mark over the past two seasons, with 5.4 walks per nine innings.
The Mets can now place Montero on the 60-day disabled list, freeing up a 40-man roster spot without exposing him to waivers, as they would have had to do had they cut him from big league camp. He will earn a full year of Major League service time, making him arbitration-eligible for the first time next winter, at which point the Mets could part ways with him.

At the very least, Montero is no longer a 2018 bullpen candidate, further clearing the Mets' roster picture. In addition to Jeurys Familia, AJ Ramos, Jerry Blevins and Anthony Swarzak, all of whom are under guaranteed contracts for 2018, Seth Lugo, Robert Gsellman, Paul Sewald and Jacob Rhame are all likely to make the bullpen. The only other relief candidate left in camp is Hansel Robles, who owns a 9.26 ERA this spring. The Mets could also choose to carry seven relief pitchers instead of eight, which would likely force Rhame to the Minors.
"We're still wanting to see some things from some guys just to make these final couple of decisions that we have to make," Callaway said. "Everybody's in a good spot. They're making it hard on us. I don't think we can go wrong with whatever we choose to do, so that's the good part of it. The bad part of it is we're going to have to give somebody some disappointing news."