SAN DIEGO -- It's not technically a six-man rotation. But the Padres have made it very clear they're going to rely on more than five starters to get them through the 2019 campaign.

Since the start of the season, no member of San Diego's rotation has missed a turn. Yet, the club has still found a way to sprinkle in starts from Triple-A callups like Cal Quantrill and Pedro Avila. Quantrill, ranked as the club's No. 10 prospect by MLB Pipeline, gets the opportunity again on Sunday.

With the Major League-youngest starting five, the Padres have made a concerted effort to limit the workloads on their pitchers -- specifically Chris Paddack and Matt Strahm, who are pitching in their second season back from major surgeries.

As a result, the Padres have made sure to give Strahm and Paddack an extra day of rest between starts. They've started on five days' rest every time they've pitched.

That's where Quantrill comes in. His start for Sunday's series finale against the Pirates comes during a stretch of nine games in nine days. It pushes Paddack's turn in the rotation to Monday and Strahm's to Tuesday.

Barring something unforeseen, Quantrill will probably be optioned following his start. The Padres have the next two Thursdays off, and they'd be avoiding four days' rest for everyone except Joey Lucchesi. They're fine with Lucchesi going on normal rest.

But if Quantrill performs well, his number might get called again -- and soon. Beginning on May 31, the Padres play 19 games in 20 days. Fellow prospect Logan Allen could get a chance, too, if he bounces back from his up-and-down start to the season in El Paso.

"It takes on a lot of importance," manager Andy Green said of the organizational rotation depth. We've needed Cal, and Pedro Avila, too, to come up and make sure our guys get the right kind of rest. And [they] slot in and give us a chance to win a game at the same time. Those guys are huge parts of this club."

That’s true, even if they aren't regularly on the 25-man roster, Green said. Quantrill made his first five starts this season at Triple-A El Paso. Then, he was called up in early May for two big league starts in which he allowed four runs over 10 innings.

Quantrill was optioned to El Paso, where he made one more start. Then, he arrived back in San Diego on Saturday afternoon. The Padres will need to make a roster move to clear space for him on Sunday.

"He should look at it as a great opportunity," Green said of Quantrill's spot start. "... He'll have to perform. As he performs more and more, he'll get more opportunity. Up to this point, we like the bulldog mentality we've seen in him."

Worth noting
• Righty reliever Trey Wingenter threw a simulated inning on Saturday afternoon at Petco Park. It marked the first time Wingenter had faced hitters since he landed on the injured list two weeks ago with right shoulder inflammation.

"Everything felt good," Wingenter said. "It feels normal, and I'm back to normal. It was nice facing hitters today. I feel like a baseball player again."

Wingenter had emerged as the bridge to the back end of the Padres' bullpen this season. He owns a 2.93 ERA and a sub-1 WHIP in 15 1/3 innings. If, indeed, Quantrill is optioned on Monday, it might be Wingenter who gets activated in his place. Or, if the Padres find themselves in need of immediate bullpen help, Wingenter might get called up as soon as Sunday.