Mets leftfielder Michael Conforto holds his left shoulder as he...

Mets leftfielder Michael Conforto holds his left shoulder as he is brought into the clubhouse by the trainer on Aug. 24, 2017 at Citi Field. Credit: Joseph D. Sullivan

WASHINGTON — Until a fateful moment of agony on Thursday afternoon, Michael Conforto had swung and missed hundreds of times as a major-leaguer. Rarely did any of those instances warrant further mention.

Then came swing and miss No. 513, one that at least one shoulder specialist believes has the potential to alter the trajectory of a promising career.

One day after Conforto dislocated his left shoulder — and tore the connective tissue that gives the critical joint stability — even longtime baseball people failed to come up with comparable scenarios. Now uncertainty clouds what had been a bright future.

“It’s just a pile-on, basically,” Mets manager Terry Collins said. “It’s certainly a devastating blow to the club, but we’ve had several. We’ll put somebody else’s name in the lineup and move forward, but certainly this is a tough one because he was having such a great year.”

Through a spokesman, general manager Sandy Alderson declined to comment, at least until Conforto is clinically examined on Monday. Otherwise, the team released no new information after its acknowledgment on Thursday night of an MRI that showed a tear in the posterior capsule of the shoulder.

The Mets left open the possibility of surgery as an option. Conforto also could rehab the injury. But Dr. Armin Tehrany, a shoulder specialist and founder of Manhattan Orthopedic Care, believes surgery is the most likely outcome.

The nature of the injury — coming on a mundane event such as a swing and miss — raised more red flags.

“The problem in this case is that this player dislocated his shoulder without any major trauma,” said Tehrany, who has not personally treated Conforto. “It was his non-dominant arm. He was just swinging a bat. And that alone led to the dislocation, which means that the likelihood that it happens again after he heals is very high.”

The Mets have not released any estimates regarding a timeline for a return. Tehrany believes that surgery could sideline Conforto for four to six months. But as is the case with any injury, even an operation carries no guarantees.

Said Tehrany: “It’s quite possible that no matter how well the surgical repair occurs, no matter how well he rehabilitates, he may never be able to get to that same level.”

Conforto, 24, was in the middle of an All-Star season. He was hitting .279 and already had established career highs in homers (27) and RBIs (68). The success came after struggles last season led to multiple demotions, and his breakout came after he began this season on the bench.

Before Friday’s game, Conforto officially was placed on the disabled list. Now he faces the potential of a delicate rehab process regardless of whether he actually undergoes surgery. His biggest challenge might be avoiding another injury.

“Moving forward regarding prevention, that’s difficult because the motion that led to the tear, which is a swinging motion, is one that he’s going to continue to do,” Tehrany said. “Because he’s continuing to do it, we always have to know that there’s a significant chance that he can eventually damage it again the same way he did the first time.”

Collins hinted that Conforto has dealt with shoulder issues in the past, making it possible that the outfielder might be more vulnerable to problems.

“It is common for someone to be naturally loose-jointed, and that does increase the susceptibility to instability,” Tehrany said. “I’d surmise that what’s happened is that he’s naturally a loose-jointed person. That’s why such a simple thing as a swing led to this tear.”

But the specialist also noted that overuse — a reality of the preparation required to first reach and then ultimately stay in the big leagues — might have been a factor.

“Oftentimes, we want to blame something,” Tehrany said. “And the truth is it’s just overuse. And the right thing to do is to rest and rehabilitate after the proper surgery and give it another try.”