SAN DIEGO -- Nick Margevicius' excellent April gave way to a rough May, and after the worst start of his young career Saturday night, the rookie left-hander was optioned to Double-A Amarillo on Sunday.

Margevicius' demotion meant opportunity for right-hander Cal Quantrill, who was promoted. Meanwhile, Trey Wingenter was activated from the injured list after missing two weeks with right shoulder inflammation, while fellow righty reliever Gerardo Reyes was optioned to Triple-A El Paso.

Quantrill -- who was beaten out by Margevicius for the final rotation spot after Spring Training -- allowed five runs in five innings Sunday. He had a chance to stake his claim to a more permanent place in the starting rotation, and he didn’t seize it, allowing four runs in the top of the first.

“There’s opportunity everywhere,” said Quantrill, whose ERA jumped to 5.40 over his three starts this year following Sunday's outing. “If you perform, you’ll stay. If you don’t perform, you’ll leave. Today, I didn’t do enough. … A 4-0 deficit is not good enough.”

On three occasions, the Padres have called up prospects for spot starts to give their regular starting five extra rest. But until Sunday, they'd used the same starting five for the entire season. Margevicius' demotion will change that -- though manager Andy Green wouldn’t firmly commit to another start for Quantrill.

Green noted that San Diego had always planned a period of rest for Margevicius, a 22-year-old unaccustomed to a big league workload. The timing isn’t exactly coincidence, but it’s not an indictment on the young left-hander either.

“This is a designed period for him to rest and to shorten his season a little bit,” Green said. “Everybody's got a plan here, and this is part of his plan this year. … He does have some things to work on. The last couple outings haven't been what we wanted and what he wanted them to be.”

Margevicius’ “plan” raises questions about the other young starters in the rotation -- like, say, Chris Paddack. The 23-year-old right-hander pitched fewer innings than Margevicius last year, and the Padres have expressed a desire to limit his workload as well. But Green wouldn’t say whether San Diego has a similar reprieve planned for Paddack, who’s quickly becoming the staff ace.

“Everybody's plan is a little bit different,” Green said. “Everybody's plan is a little bit unique. This is part of Nick's plan.”

In six March/April starts, Margevicius posted a 3.23 ERA, but that mark rose to 8.59 in May. Perhaps big league hitters began figuring out his diverse pitch mix. Margevicius' high-80s fastball doesn't quite work when he isn't hitting his spots, too.

Margevicius' command is generally pinpoint. It's been anything but that over his last three starts. Margevicius allowed four homers and six runs in a loss to the Pirates on Saturday night.

"It's something I'm going to go back this week and work on," Margevicius said Saturday night. "You get up here, and it's not so easy. ... It's a rough spot for me, but I'm going to work my way through it."

As for Wingenter, his return provides a crucial bridge to the back end of the Padres' bullpen. He'd posted a 2.93 ERA and a sub-1 WHIP in 15 1/3 innings.