SAN DIEGO -- The Padres placed right-hander Chris Paddack on the injured list ahead of Friday's game against the Giants, though the team did not offer an explanation for his presence there.

Right-hander Miguel Diaz had his contract selected from the alternate training site and joined the team Friday as Paddack's replacement on the roster.

"I can't really disclose a lot of information with that," said Padres manager Jayce Tingler. "It's a medical condition."

Paddack had posted a 5.40 ERA in five starts this season, though his 3.22 FIP would indicate that he's been better than his numbers indicate. Paddack is coming off a particularly sharp outing in Arizona in which he didn't allow an earned run until the sixth inning -- when he came undone and surrendered three.

As for Diaz, he was once a highly regarded weapon in the Padres' pitching plans after his selection in the 2016 Rule 5 Draft. But he has dealt with a handful of ailments since then, notably two major knee injuries, and has only made 16 appearances since 2018. He owns a 6.62 ERA across parts of three big league seasons.

Weathers, Lamet day to day
Paddack isn't the only pitcher whose return to the rotation is uncertain. Right-hander Dinelson Lamet is on the IL after experiencing right forearm tightness in his start against the Brewers last week. Lefty Ryan Weathers exited his outing Wednesday with symptoms of "dead arm" and "fatigue," Tingler said.

With Paddack out, the Padres wouldn't have a full rotation even if Weathers and Lamet were able to make their next starts, as the team hopes. But Tingler wasn't ready to commit to that on Friday.

"Both guys are progressing and seem to be doing better each day, but we haven't set a timetable or we don't have a date for them to start," Tingler said. "So I would have to call both guys day to day."

Weathers, perhaps notably, has not been placed on the IL. After the southpaw's start lasted only one inning on Wednesday, Tingler indicated there was a strong chance Weathers would get the ball for his next outing. Team doctors are confident he sustained no ligament damage.

As for Lamet, he threw an aggressive bullpen session on Wednesday, which could have him lined up to pitch Sunday against the Giants. But since Lamet is coming off a UCL strain last October, the Padres certainly aren't going to rush him back into action.

The crux of the Padres' rotation question is this: They need two starters for their three games from Sunday through Tuesday. Joe Musgrove will get the ball in one of them. The other two spots are up for grabs.

Nola returns
Padres catcher Austin Nola is expected to make his first start behind the plate on Saturday night with Blake Snell on the mound. Nola was activated just before Wednesday's game against the D-backs, and he served as a pinch-hitter while Victor Caratini made the start. Caratini started again on Friday, as Yu Darvish's personal catcher.

Nola missed the first four weeks of the season with a fractured left middle finger. The Padres have sorely missed his production both at the plate and behind it. He posted a .273/.353/.472 slash line in 48 games with the Mariners and Padres last season.

Nola was presumed to be San Diego's regular catcher, but Tingler noted that -- at least at the outset of the season -- he and Caratini will likely share starts relatively evenly, while Nola builds his workload. The 31-year-old's return took a bit longer than expected, as the inflammation in his finger subsided slowly. It’s a particularly tricky injury for a catcher who receives every pitch with his left hand.

"That middle finger can always be in the action," Nola said. "We just had to make sure we took it slow and let it heal before we went full-swing at it.