MINNEAPOLIS -- The Twins' bullpen is finally whole again.

Cody Stashak returned from an extended stint on the 10-day injured list with lower back inflammation on Monday, while the Twins optioned Devin Smeltzer to the alternate training site in St. Paul, Minn., in a corresponding move. Stashak had last pitched on Aug. 11 and missed 23 games with the injury.

Twins manager Rocco Baldelli said that there isn't much concern about any lingering pain or discomfort. When Stashak first went on the IL in August, Baldelli had said that Stashak had been pitching through discomfort throughout the 2020 season in 2019.

Even so, the rookie right-hander had pitched to a 3.86 ERA in seven innings this season, including 10 strikeouts and two walks. The 26-year-old had gained trust in the middle and late innings of close games following a strong debut season.

"I don't think we're going to send him out there and overwork him initially," Baldelli said. "I think we're going to see how he responds to everything and how recovers and comes back after his first outing, whenever that may be. But he's been feeling a lot better and I think the time off was very well-served for him."

Zack Littell was also activated from the IL on Sunday, but he was immediately optioned to the alternate training site. The Twins don't have any room in their nine-man bullpen at the moment because of strong performances from Jorge Alcala and Caleb Thielbar, who have stepped up as important depth pieces alongside the seven-man core of Taylor Rogers, Tyler Duffey, Trevor May, Tyler Clippard, Sergio Romo, Matt Wisler and Stashak.

The Twins ran with a 10-man bullpen for much of the season, but they need the positional depth right now due to their measured usage of Josh Donaldson, Byron Buxton and Luis Arraez.

Sanó continuing improvement at first base
According to Twins third-base coach and infield coordinator Tony Diaz, the club's internal metrics indicated that Minnesota's infield defense ranks in the top 10 in the league and is much improved from last season. Much of that is due to the continued work on first step with Arraez, Jorge Polanco and other defenders, but Miguel Sanó's transition to first base is also an important component.

It certainly hasn't been a seamless transition to first base for the big man; FanGraphs measures Sanó's defensive contributions at minus-4 defensive runs saved, and his minus-0.9 ultimate zone rating also paints him as a below-average defender.

With that said, the eye test paints a mixed bag of Sanó's defensive contributions, too. The range has admittedly been an issue at times because of the lack of instincts and experience, particularly in shifted infields, where he sometimes charges balls he should leave to the second baseman and acts too aggressively on other grounders.

Still, Sanó generally makes all of the plays he should make as a receiver, and his ability to pick bad throws has been particularly impressive to Diaz, and the skill set gives Diaz reason to believe Sanó will continue to improve.

"I think he needs to continue to improve on the spacing aspect of getting to the bag on time, knowing his surroundings, where the shift is, where the second baseman is, at all times," Diaz said. "Whether to charge a ball, the 'tweener between him and the pitcher, those things are going to come with experience."

Injury notes
• Nelson Cruz sat a second straight day with hip soreness that has lingered for several days. Baldelli hopes that Cruz will be ready to play Tuesday's doubleheader in St. Louis.

• Sanó experienced mild hamstring soreness during Sunday's game and was not in Monday's lineup, with LaMonte Wade Jr making his second career start at first base.

• Mitch Garver (right intercostal strain) has been swinging a bat and should ramp up to catching in simulated game situations later this week.