ST. LOUIS -- Left-handed reliever Andrew Miller was placed on the 10-day injured list, retroactive to Monday, with left shoulder fatigue, the Cardinals announced before Thursday’s doubleheader against the Pirates at Busch Stadium. Manager Mike Shildt said it’s “nothing structural,” and he expects Miller to be ready to return in a week after resting.

Miller has appeared in seven games (5 2/3 innings) this season -- seven games short of vesting his option for 2021. He hadn't been available for the last three days, as he was still building up strength after the Cardinals’ long layoff earlier this month. The move to the IL allows him to recover completely while giving the Cardinals extra help in the bullpen. The 35-year-old has a 4.48 ERA in two years with the Cardinals, who signed him in 2018 to be their high-leverage, left-handed option out of the bullpen after successful years as the Yankees' and Indians' closer.

“Just a recovery thing,” Shildt said. “He’s been a warrior and just was honest and said, ‘I could probably keep going and pushing through it,’ but I think we’d all feel better if we could get it behind him. We’re pretty comfortable that that week will take care of him being able to get back and having the strength and the capability to finish the season.”

His appearances with the Cardinals this year designated him as their closer, and that role could shift to Giovanny Gallegos as Miller recovers. Lefty Austin Gomber could also see some higher-leverage, late-inning situations in the next week.

“In general, I’ve been super pleased with how the guys have recovered,” Shildt said. “We’ve done our part to take care of them as best as possible. We’ve listened to them; we’ve stayed away from guys in spots that we would have liked to have had them. But we’ve said from the beginning that we’re going to take care of our guys to the best of our capability. We know guys have to pitch and play, and they get it too, but just coming back -- and again, [Miller’s shoulder is] nothing structural we don’t feel like. Just a little fatigue.”

In a corresponding move, the Cardinals activated right-hander Junior Fernández from the COVID-19 injured list and added him to the active roster. Shildt said Fernández threw a 25-pitch live batting practice Tuesday to be built up for a return.

The club also activated infielder Edmundo Sosa off the COVID-19 injured list and will have him stay at the Cardinals’ alternate training site in Springfield, Mo. Right-hander Seth Elledge is Thursday’s 29th man for the doubleheader. Fernández and Sosa were two of the eight remaining players still working their way back from testing positive for COVID-19 during the Cardinals’ outbreak.

The Cardinals have 46 players on their 40-man roster because players on the COVID-19 injured list do not have to count against that number. Because the Cardinals now have six remaining players on the COVID-19 injured list -- including starter Carlos Martínez and reliever Ryan Helsley -- they will have to make a transaction on the 40-man roster and 60-man player pool when and if those players return. With the Aug. 31 Trade Deadline rapidly approaching, a transaction could include trading a player on the 40-man or placing a player on waivers in hopes they pass through the 29 other teams.