Perdomo, the 22-year-old Rule 5 Draft pick who hasn't pitched above Class A, got his first appearance of the spring against the Mariners and allowed two runs in his one inning.
Both runs came on a home run to left field by Chris Iannetta in the second inning of the Padres' 7-0 loss to Seattle at the Peoria Sports Complex.
Perdomo allowed two hits with one walk and also picked a runner off second base.
"Today wasn't a great day, but I'm going to keep working hard to make the most of every opportunity I get," Perdomo said through a translator.
Perdomo is one of four Rule 5 players on the roster this spring -- pitchers Blake Smith, Josh Martin and outfielder Jabari Blash are the others. The four have to stick on the 25-man roster all season or be offered back to their original teams.
Perdomo has the largest ceiling of all four and is the youngest. But can the team reasonably expect to carry him all season, even though he would have likely been a candidate to open the regular season at the Double-A level?
San Diego first-year manager Andy Green wasn't about to let Wednesday's outing temper his enthusiasm for Perdomo.
"He threw early side sessions that looked very good," Green said. "He was down in the [strike] zone, attacking very well. As he has faced live hitters, he's gotten a little jumpy, front side flying [open], arm trailing a little bit and the ball elevated a little bit was the result of what you saw today.
"But he's not going to be far off. We're going to get that corrected. He's squarely in the mix to do something."
Perdomo opened the second inning by getting Adam Lind on a ground ball. He then allowed a single to Seth Smith, followed by the home run to Iannetta on a pitch he would have liked to have back, a 2-2 slider.
"I'm really just following what the catcher called. I would have liked to probably go with another fastball there," he said. "… I would have liked to have thrown another pitch, but it is all part of the learning process."
That's a process that will continue all spring, as the Padres won't likely be in any hurry determining if Perdomo can, or will, make the roster.
"It's really been a great experience being around these guys, asking them questions," Perdomo said. "I always try to ask questions and learn from them. I'm going to keep working on my pitch sequences."