BOSTON — The All-Star break did nothing to cure the Yankees’ injury ills.

General manager Brian Cashman dropped a bombshell early Friday afternoon, disclosing that righthander Michael Pineda has been diagnosed with a partial tear of his right ulnar collateral ligament that likely will require Tommy John surgery.

Cashman said Pineda, 28, who met with Dr. Timothy Kremchek on Friday in Cincinnati, will seek a second opinion before determining his next step. Regardless, Pineda, a free-agent-to-be who is 8-4 with a 4.39 ERA this season, is done for the season and might have thrown his last pitch as a Yankee.

“It was a shock to me,” Joe Girardi said. “It was devastating for him.”

Cashman said Pineda, 31-31 with a 4.16 ERA in his four seasons as a Yankee, did not complain of any discomfort in his elbow until the ninth inning of a game two days after his July 5 start, mentioning something to trainer Steve Donohue.

For now, Cashman will fill the hole created by Pineda’s injury internally, and he did not rule out top pitching prospect Chance Adams as a candidate. The 22-year-old righthander is 6-3 with a 2.50 ERA with Triple-A Scranton/Wilkes-Barre after earning a May promotion from Double-A Trenton.

Girardi didn’t discount the possibility of Adams getting a shot but noted his command issues: 22 walks in 57 2⁄3 innings. “We still feel he has some work to do,” Girardi said.

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One opposing team scout who covers the Yankees’ system agreed to a point but nonetheless said Adams is polished enough. “He’s been major league-ready all year,” the scout said. “Plus fastball and changeup, with two average breaking balls [curveball and slider]. All you want in a starter.”

For now, righthander Bryan Mitchell will take Pineda’s turn, starting the first game of Sunday’s doubleheader. Luis Severino will start Saturday afternoon and Masahiro Tanaka will go Sunday night.

Cashman was engaged with the White Sox on lefthander Jose Quintana — who was dealt to the Cubs on Thursday — but found the price tag too high in terms of the high-level prospects Chicago wanted. He said he will continue to be “aggressive” in the marketplace, but not at the expense of the future.

Even with his team staggering a bit, having lost 18 of 25 going into the break and about to embark on a three-city, 11-game trip, Cashman said the Pineda news doesn’t turn him into a seller. “I’ve been trying to add, not subtract,” he said. “That information [regarding Pineda], as bad as it was, did not [change that].”

Pineda, part of what was thought to be a blockbuster trade before the 2012 season — he came to the Yankees in a deal in which Jesus Montero was sent to the Mariners — got off to a terrific start this season. He was 6-2 with a 3.32 ERA through May. Then he stumbled, going 2-2 with a 6.14 ERA in his last seven starts, including what turned out to be his final one, July 5 against the Blue Jays, when he allowed three home runs in three innings in a 7-6 loss.

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As for some of the other injured Yankees, Cashman said he doesn’t expect Greg Bird, out most of the season with a right ankle bone bruise, to be a significant contributor the rest of the year. He saw another specialist last Monday who determined that Bird might have a condition called os trigonum syndrome, essentially excess bone growth in the foot area. The initial plan was to try to get Bird through the season with Novocain and cortisone shots, but Cashman said surgery “is a very real possibility.” Such a surgery would require six to eight weeks of recovery time.

Matt Holliday, out with a viral infection, returned to the lineup Friday night. Girardi said he expects Starlin Castro, out with a hamstring strain, to rejoin the Yankees on Saturday.