PITTSBURGH -- Nick Tropeano, a late scratch from his scheduled Saturday start at PNC Park, has been placed on the 15-day disabled list with tightness in his shoulder, becoming the fifth Angels starting pitcher currently tending to an injury.
Tropeano initially felt discomfort on Sunday -- when he gave up four runs on seven hits and five walks in five innings against the Astros -- and it continued in a between-starts bullpen session three days later. An MRI on Saturday morning revealed no structural damage.
Tropeano believes he can be ready by the time his DL stint is up, on June 14.
"Oh yeah," he said, "a hundred percent. I think I just needed a couple of days, and we weren't able to buy those few days. Just one of those things."
The Angels were off on Thursday, allowing them to move their four healthy starters up a day and keep them on a normal five-day schedule. Jhoulys Chacin filled Tropeano's spot on Saturday. Hector Santiago will start on Sunday and Matt Shoemaker will follow on Monday, the opener from Yankee Stadium. 
The Angels need a starter on Tuesday and Sunday, June 12, which just so happens to be in line with Tim Lincecum's schedule. Lincecum could potentially make the latter start, but he will pitch for Triple-A Salt Lake this coming Tuesday, Angels manager Mike Scioscia confirmed.
Prospect Nate Smith, ranked third in the Angels' system by MLBPipeLine.com, also can't start because he pitched on Friday, carrying a no-hitter into the ninth inning. The Angels also have Kyle Kendrick and Chris Jones as available starting-pitching depth in Triple-A. Another option would be a bullpen game. The club recalled reliever Deolis Guerra from Triple-A to give the bullpen an extra arm with Tropeano on the DL. 
Scioscia, who would not reveal his upcoming pitching plans, said Tropeano's shoulder is "just a little tight."
"It's going to take four or five days, maybe, to get it to where he can go out there and throw a 'pen and test it," said Scioscia. "We want to err on the side of caution and just give him enough time to get where he wants to be."
Tropeano didn't inform the team about his shoulder pain -- one he continually called "discomfort" -- until a couple of days after his last start, when he entered the trainer's room asking for treatment. The 25-year-old right-hander initially thought it was "just one of those valleys" starting pitchers go through during a season, but he didn't feel right when he got off a mound the following day.
By the time he played catch early Friday afternoon, Tropeano pretty much knew the shoulder issues would cost him at least one start.
The Angels' rotation is down to four starters -- Chacin, Santiago, Shoemaker and Jered Weaver.
Garrett Richards and Andrew Heaney are hoping stem-cell therapy will heal their torn ulnar collateral ligaments, but they won't return until August at the earliest. C.J. Wilson was shut down after his first rehab start because of what the team called biceps tendinitis. And Tyler Skaggs, coming off an encouraging outing in extended spring, is still more than a week away from restarting a rehab assignment.
Tropeano carries a 3.25 ERA through his first 10 starts and has limited his opponent to three runs or fewer eight times.
"I want to be out there and pitching, and it took every ounce of my energy to go in there and say a little something," Tropeano said. "But we all thought it was the best idea."