SAN DIEGO -- Luis Perdomo's 2018 season might be on its last legs.
The 25-year-old right-hander was placed on the disabled list Saturday with right-shoulder soreness that has been worsening over his past couple of starts. Perdomo did not inform the team of the ailment until after Friday's 6-2 loss to Arizona. He underwent an MRI on Saturday, and the club is awaiting results before placing a timetable on his return.
"It was something I was trying to work through, something I was trying to fight through to make sure I could be up here," said Perdomo. "Up until now, it had been fine, but I couldn't really take it much longer."
The Padres recalled lefty reliever Jose Castillo in his place. They'll need to make another move for a starter when Perdomo's spot in the rotation comes up again -- likely Thursday in Chicago.
It's the third time in the past two seasons that Perdomo will miss time with a shoulder ailment. In each of the previous two, he returned shortly after the minimum stint on the disabled list. Perdomo said this version of his injury feels similar, but slightly worse, and he noted that he may have rushed back too quickly from the last one.
"The hope is it doesn't set him back too long, but we need to figure out what is recurring and why it's recurring," said Padres manager Andy Green. "We're taking a look today and hoping it's nothing too serious. … If it keeps coming back, it's probably something underlying that we need to address. That's the reason for the testing."
Green expressed disappointment that Perdomo hadn't informed the training staff earlier. But he added that he understood Perdomo's sentiment, given that he was fighting for a place in the big leagues and had only recently been recalled.
In any case, it's been a disappointing 2018 campaign for Perdomo, who has a 7.94 ERA in nine starts. A Rule 5 Draft acquisition before the 2016 season, Perdomo's development -- or lack thereof -- has been maddening for the Padres. Once believed to be a cog in the club's rotation of the future, Perdomo has mostly spun his wheels for two seasons.
"[The frustration] is pretty high," Perdomo said. "I want to be able to show what I can do."
As for his rotation place, the Padres have a handful of options. Jordan Lyles is rehabbing right elbow inflammation at Triple-A El Paso, though he's expected to require one more outing there. Robbie Erlin or Matt Strahm could shift from the 'pen to the rotation, at least temporarily.
But the likeliest candidate might be El Paso right-hander Brett Kennedy, who lowered his ERA to 2.56 with six innings of two-run ball on Friday night. Kennedy is not on the Padres' 40-man roster, nor is he a highly touted prospect. But he's been one of their best Minor League arms this season, and the club is eager to give its high-level pitchers a big league opportunity as the season winds down.
"We've got a lot of choices," Green said. "... We've got some younger guys who are throwing the ball really well. Brett Kennedy had another really good outing yesterday. Those guys are catching our attention, and some of those guys' time is going to come very soon."
Of course, Tuesday's non-waiver Trade Deadline could further alter the Padres' pitching plans. In that regard, the off-days on Wednesday and Aug. 6 fall kindly for Green.
In theory, Green could use a four-man rotation until Aug. 11. But that runs counter to the Padres' desire to give extra rest to their young starters, while also giving opportunity to untested Minor League pitchers -- like Kennedy, perhaps.