NEW YORK -- The Yankees will be without Michael Pineda for longer than anticipated, as the right-hander ended his simulated game on Tuesday after just one inning when he felt tightness under his pitching arm.
Following an MRI exam, team physician Christopher Ahmad diagnosed Pineda with a Grade 1 strain of the teres major muscle in his upper back. The Yankees said that Pineda will be shut down from activity for 10 days, and the injury will cost him three to four weeks.
Pineda is currently on the restricted list, serving a 10-game suspension after being ejected for having pine tar -- an illegal substance -- on his neck in last Wednesday's game at Fenway Park.
That suspension is slated to end next Monday, when the right-hander was expected to pitch against the Angels in Anaheim. Yankees general manager Brian Cashman said late Tuesday that he is looking into how the team will satisfy Pineda's suspension with his upcoming trip to the disabled list.
Pineda is 2-2 with a 1.83 ERA in four starts this season, having rung up 15 strikeouts against three walks in 19 2/3 innings. He did not pitch in the big leagues during the 2012 and '13 campaigns because of right labrum surgery.
Earlier on Tuesday, Girardi said that the club will continue to use David Phelps as a spot starter while Pineda is unavailable. Phelps owns a 3.86 ERA in nine relief appearances this season. He is scheduled to start on Wednesday against the Mariners and will be asked to throw 70-75 pitches.
Bryan Hoch is a reporter for MLB.com. Follow him on Twitter @bryanhoch and read his MLBlog, Bombers Beat. This story was not subject to the approval of Major League Baseball or its clubs.