Pineda seemed to be on the verge of tears as he talked to reporters following his 2 2/3-inning outing against the Phillies at George M. Steinbrenner Field, in which he permitted six runs and seven hits and showcased little command of his fastball.
The MRI on Saturday showed Pineda has right shoulder tendinitis, manager Joe Girardi told reporters in Kissimmee, Fla. on Saturday morning. Pineda will be placed on the 15-day disabled list and the Yankees figure to treat him conservatively, but all things considered this is good news, considering the worst-case scenarios.
"It's great news, for what your biggest concerns are," Girardi said. "It just needs a little rest. He'll get treatment and then we'll see how long until he picks up a ball. We'll be a little conservative."
The injury to Pineda ended any questions of who will be in the rotation. Girardi said that the order will be CC Sabathia, Hiroki Kuroda, Phil Hughes, Ivan Nova and Freddy Garcia.
Asked to pinpoint the area that bothered him, Pineda pointed to the back of his right shoulder. Pineda said that it is just "normal" soreness, but Yankees general manager Brian Cashman wanted Pineda to have an MRI.
"Anytime a pitcher talks about his shoulder, I have concern," Cashman said Friday. "His velocity is down, so you put those two together, it definitely causes concern."
The Yankees have repeatedly asked the 23-year-old Pineda if he feels healthy this spring, spurred by a noticeable dip in his radar gun readings. He was clocked mostly at 91 to 92 mph on Friday, maxing out at 94, which Girardi said is about where Pineda has resided all spring.
"Today my arm is a little sore. Most of the time, it's not," Pineda said. "When I'm throwing, it's a little sore. It's normal. Sometimes every player doesn't feel 100 percent if they play every day, you know?"
Pineda said he told the Yankees about the soreness after he was lifted from the game. He said that he had tried to throw harder on Friday and also may have been flying open with his left shoulder in his delivery, causing his fastball to run.
"I don't know. I tried to pitch my game," Pineda said. "I tried to throw harder today. I don't know what was my velocity. I tried a couple of times."
Earlier this spring, Pineda deflected questions about his velocity by saying he was "conserving" energy before trying to get back up to the levels of 95 to 97 mph that so enticed the Yankees to acquire him from the Mariners.
"We've asked him all spring and he's said he's been fine," Cashman said. "But it's not like I sat him down now, stuck a light in his face and said, 'Tell me now; in the last five weeks'. ... I don't know.
"I know we've asked him all spring and he's said he's been fine, that he's healthy and feels good. Tonight, after he came out of his start, he talked about his shoulder being tight in the back."
Girardi said that Pineda had consistently also told him that he was not having any problems.
"We've talked about it, and he's said he feels good," Girardi said. "We've talked about how he's worked on his changeup really hard. This is the first we've heard of [stiffness]. He did all his sides and he did all his work."
Pineda was acquired by the Yankees from Seattle with Minor League pitcher Jose Campos in January as part of a blockbuster trade of promising prospects that sent catcher/designated hitter Jesus Montero and pitcher Hector Noesi to the Mariners.
Cashman said that he did not believe Pineda's velocity issues dated back to his time with the Mariners, save for a late September start he made on extra rest after being held out for innings concerns. What the Yankees are dealing with now appears to be new.
"In terms of his mechanics, everything else like that, the only thing that has obviously been a red flag has been the velocity," Cashman said.
Pineda expressed confidence that he can get back to the success form he showed last year, when Pineda was 9-10 with a 3.74 ERA in 28 starts for Seattle -- including an 8-6 record with a 3.03 ERA in 18 first-half starts.
"I think I'm the same Michael Pineda," he said. "I'll make my adjustments and that's it. I'm pitching, you know? I'm not worried about that. I'm the same Michael Pineda from last year."
Bryan Hoch is a reporter for MLB.com. Follow him on Twitter @bryanhoch and read his MLBlog, Bombers Beat. MLB.com reporter Paul Hagen contributed to this report. This story was not subject to the approval of Major League Baseball or its clubs.