"Wasn't a shoulder separation, so that's the good news," manager Buck Showalter said. "But he's got some fibers he tore in there and some strain up in the shoulder. Good news is it's his left shoulder.
"When I left [Sunday], Robert said, 'I'll see you in Minnesota,' and today he's on the DL. The doctors are pretty sure that he can be [out] as long as 3-4 weeks."
Andino will be placed on the disabled list on Tuesday, with starter Zach Britton taking his roster spot.
His absence is another blow for an already-depleted Orioles team. Baltimore's Opening Day second baseman, Andino is batting .230 with five home runs, 21 RBIs and four stolen bases in 79 games, having taken over full-time duties in the absence of veteran Brian Roberts, who is out with a right labral hip tear.
Andino was injured in the sixth inning of Sunday's game while diving for Alex Avila's RBI single off starter Miguel Gonzalez, which gave Detroit a 3-0 lead. Andino dove to his left and stayed down after the ball went into right field. He later exited the game, with X-rays coming back negative.
The 28-year-old Andino stayed back in Baltimore and was put in a sling, according to Showalter, who also said that Andino will report to the team's spring facility in Sarasota, Fla., after a few days of rest to let the injured area calm down.
The initial timetable is 3-4 weeks, and while the injury isn't on his throwing side, Andino will still need to get some at-bats with one of the team's Minor League affiliates before he is activated.
Who will now take over at second base? Internally, Steve Tolleson and Ryan Flaherty are the two logical options, with Tolleson getting the start in Monday's series opener against the Twins.
Tolleson, who came up through the Twins Minor League system, last played second base in the Majors in 2010, while Flaherty is a Rule 5 Draft pick whom the Orioles have used sporadically.
There's also a chance the Orioles could look externally, especially given that Andino was already the team's backup to Roberts. Showalter didn't rule out that possibility.
"That'd be a good question for [executive vice president of baseball operations Dan Duquette," Showalter said. "I am looking from within. We got a club playing real well down in [Triple-A] Norfolk and when we have a need, which we don't currently have, that's where I'll look. See where it takes us."
Brittany Ghiroli is a reporter for MLB.com. Read her blog, Britt's Bird Watch, and follow her on Twitter @britt_ghiroli. This story was not subject to the approval of Major League Baseball or its clubs.