SAN DIEGO -- The inflammation in Luis Perdomo's right shoulder has subsided, and the 23-year-old right-hander will return to the mound Sunday, making his first appearance since he started the Padres' home opener.
Perdomo said he began to feel soreness in his shoulder during Spring Training. But it didn't truly flare up until after his start against the Giants at Petco Park. He approached the Padres about the ailment during his next bullpen session.
"It first started in Spring Training," Perdomo said through a team interpreter. "I was working through it. Now that I've been on the DL, working with our trainers, working with those guys, it's been feeling a lot better."
Understandably, concerns were raised when the Padres placed Perdomo on the disabled list with shoulder inflammation. The move came a year to the day after they did the same with Tyson Ross.
At the time, the Padres believed the decision to DL Ross was mostly precautionary. Ross ended up missing the entire season.
"With shoulders -- last year we found out with Tyson -- sometimes you just don't know," said Padres manager Andy Green. "But this was more a case, now, of a young man that had never felt anything in his life, [who] felt something very minor. He paid attention to it and now he's going to be ready to pitch again."
Perdomo threw an extended bullpen session of about 50 pitches Wednesday. Having missed the past two weeks, he said he approached his 'pen with more of a game-like feel.
"As I went through it, I was going through it and focusing on it more like it was a game," Perdomo said. "That was the plan. I was just working and focusing on my pitches and making sure I'm ready for my next outing."
Perdomo was arguably the Padres' most effective starter during the second half last season. He was, without question, their most impressive starter in Spring Training.
In his first outing, he showed glimpses of what made him so effective. Last year, no National League pitcher had a higher ground-ball rate than Perdomo's 59 percent clip.
For five innings, he limited the Giants to just one run, and he induced 13 ground balls, compared with just three fly balls on the afternoon. Then in the sixth, he came undone, loading the bases before Brandon Belt hit a grand slam. Perdomo finished having allowed five runs over 5 1/3 innings.
"I felt good in that first start," Perdomo said. "Since then, it's been good spending time with teammates, being around them and getting ready to take the mound next time."
That "next time" comes Sunday at home against the Marlins, as Perdomo slots into the rotation spot left vacant by Jarred Cosart, who was placed on the disabled list with a right hamstring strain. The Padres won't reinstate Perdomo from the DL until after Saturday's game. It appears most likely they'll option one of their nine active relievers to Triple-A El Paso.