NEW YORK (CBSNewYork)The Yankees will likely be without Michael Pineda for the rest of the season after the starting pitcher was diagnosed with a partial tear of the ulnar collateral ligament in his right elbow, general manager Brian Cashman announced Friday.

Doctors have recommended Pineda undergo season-ending Tommy John surgery. The right-hander will seek a second opinion. The Yankees have already placed him on the disabled list.

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Cashman said Pineda did not mention that he was feeling discomfort in his elbow until a couple of days after his last start, on July 5.

Yankees starter Michael Pineda pitches against the Texas Rangers during the first inning at Yankee Stadium on June 25, 2017. (Photo by Adam Hunger/Getty Images)

Pineda is 8-4 this season with a 4.65 ERA. He has struggled in recent outings, going 2-2 with a 6.14 ERA over his last seven starts.

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The 28-year-old pitcher is set to become a free agent after this season.

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The injury is likely to turn up the pressure on Cashman to trade for a starting pitcher. Masahiro Tanaka has struggled all season, going 7-8 with a 5.47 ERA. Meanwhile, CC Sabathia was roughed up in his first start, on July 4, after returning from the DL with a hamstring injury.

Cashman said the Yankees will be “careful buyers” as the July 31 trade deadline approaches. He has repeatedly said he’s reluctant to sacrifice the Bombers’ top prospects.

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Other Yankees news Cashman discussed:

• First baseman Greg Bird hopes another injection in his inflamed ankle could help, but surgery is a “real possibility” to remove excess bone growth. Bird has been out since May 2. Surgery would sideline him six to eight weeks.

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Newly acquired first baseman Garrett Cooper will join the Yankees for this weekend’s series against the Red Sox at Fenway Park. The Yanks acquired Cooper in a trade with the Brewers on Thursday. He played in 75 games for the Triple-A Colorado Springs Sky Sox this season and hit .366 with 17 homers and 82 RBIs.