The 23-year-old Pineda has been diagnosed with an anterior labral tear of his pitching shoulder and is scheduled to undergo arthroscopic surgery on Tuesday. He will be out of Major League action for a minimum of 12 months, the Yankees said.
Dr. David Altchek, the Mets' team physician, will perform Pineda's procedure at the Hospital for Special Surgery in New York, assisted by Yankees team physician Dr. Christopher Ahmad.
"I'm devastated," Yankees general manager Brian Cashman said. "There's always risk involving pitchers, but this was a big move that I pursued this winter. You always go in with eyes wide open if you pursue this with pitching.
"To experience this on the front end, it's extremely difficult, but obviously even more so difficult for the player. Michael's a good kid, he's a hard worker. The last thing obviously that we want -- and that he wants -- is to have surgery, but given the circumstances, this is the best path to go now."
An American League All-Star who was 9-10 with 3.74 ERA in 28 starts for the Mariners last season, Pineda never showed his full velocity with the Yankees and admitted late this spring that he was trying to throw harder to increase the readings on radar guns.
Cashman said that he is confident the Yankees did not receive a damaged player from the Mariners in January's trade, noting that Pineda was subjected to a thorough physical that included an MRI before the deal was completed.
"In no way do I believe, or do the New York Yankees believe, that the Seattle Mariners had any knowledge of any issues here with Michael Pineda prior to the trade or anything of that nature," Cashman said. "He was a fully healthy player we acquired. We had full access to his medicals, which were clean.
"We had the opportunity to do a full physical exam, which we did, which came out clean. Michael has never had a shoulder issue nor has he complained of one with the Mariners, nor has he ever had any tests on the shoulder with the Mariners. This is just an unfortunate circumstance that can happen. It happened."
The Yankees believe that Pineda's labrum tear occurred last Saturday, because it did not show up on either of their previous MRIs. Pineda cut short an extended spring training outing in Tampa, Fla., after 15 pitches, complaining of weakness -- but not pain -- in his shoulder.
"It's unfortunate," Yankees manager Joe Girardi said. "When and where, and how, and what we did doesn't matter now. What we have to do is move forward and try to get this kid healthy."
Ahmad said that the Yankees believe that Pineda can make a full recovery without sacrificing the velocity that made him such a coveted prospect. Ahmad was encouraged that Pineda's rotator cuff is intact and not affected by the injury.
"Based on what we know from Michael's MRI scan, there is a discrete tear," Ahmad said. "We do feel that tear can be repaired arthroscopically. Based on that, we're optimistic that we can get him recovered."
Labrum tears are significant, but pitchers can and do recover. In recent years, Chris Carpenter, Trevor Hoffman, Ted Lilly and Curt Schilling have been examples of positive return stories; others, like Mark Prior, Ben Sheets and Brandon Webb, have not enjoyed such successful comebacks.
"He does have youth on his side, I will say that," Girardi said of Pineda. "And he doesn't have a ton of mileage in his arm as a younger player, so I think that bodes well for him. None of us is ever really going to know until we get to that point."
The Yankees sent top hitting prospect Jesus Montero and pitcher Hector Noesi to the Mariners for Pineda and pitching prospect Jose Campos. Montero said that he has never met Pineda, but he is sympathetic to the right-hander's situation.
"They told me that he's going to get surgery," Montero said in Detroit, where he was 3-for-5 with two RBIs in the Mariners' 9-1 victory over the Tigers. "I feel bad for him. I feel sorry. I want him to be healthy, too, and playing for the Yankees."
Through play on Wednesday, Montero is hitting .281 (18-for-64) with two home runs and 11 RBIs in 17 games for Seattle, while Noesi was 1-2 with a 9.49 ERA in three starts spanning 12 1/3 innings. Girardi said that it was too soon to discuss any buyer's remorse.
"I don't think you ever make evaluations of deals in the first year or the second," Girardi said. "I think you have to wait a long time. In 10 years, we'll all look back on it and say, 'This was a great idea, or [not].' I think it's unfair to evaluate something so early."
Cashman said that he spoke briefly to Pineda, who is understandably disappointed by his situation.
"Bottom line, I feel terrible about the situation Michael is facing right now," Cashman said. "Hopefully all this will do is delay the eventual performance that Yankees fans can be proud of in the future from Michael Pineda."