"Cody just twisted his left knee a little. I think it might have been the first [at-bat]," said Valentine, who added that he saw Ross "manipulating it" in the fifth. "I figured I'd get him out of there, get ice on it as soon as possible."
Ross said the knee was "a little sore" and that the injury was not something he had been dealing with prior to Wednesday.
Ross, who has hit a team-leading five homers, struck out on six pitches against Twins right-hander Anthony Swarzak for the second out in the sixth at Target Field. Hitting .267 on the season, Ross drove in the game's first run with a single in the first and finished 1-for-3.
Ross' importance has been magnified by injuries to Jacoby Ellsbury, Carl Crawford and Jason Repko, as any depth the Sox did have in Spring Training doesn't exist anymore.
Before the game, Valentine talked about the impact Ross and fellow outfielder Ryan Sweeney have had this season.
"It's been paramount," Valentine said. "It's been a godsend. Not that we didn't think they'd be good, but we thought collectively they'd do what they're doing individually. It's been spectacular."