MINNEAPOLIS -- The Detroit Tigers placed left-handed reliever Nate Robertson on the 15-day disabled list before Thursday's game at Minnesota and called up left-hander Luke French from Triple-A Toledo.
Robertson was put on the DL retroactive to May 6 with a muscle strain in his lower back.
Manager Jim Leyland said Robertson hurt his back while doing squats after a game at Cleveland last weekend and likely won't be ready for at least another seven or eight days.
Had the team known the injury was that serious, Leyland said, right-hander Juan Rincon probably would have stuck around a little longer. He was designated for assignment to make room for starter Dontrelle Willis, who came off the disabled list this week.
After four-plus seasons as a fixture in Detroit's rotation, Robertson has languished in the bullpen. He has a 6.30 ERA in 10 innings this season, with six walks and seven strikeouts.
French was in uniform for the first time in the majors. He went 2-2 in six starts with a 2.91 ERA and 29 strikeouts for the Mud Hens. The 23-year-old was an eighth-round draft pick in 2004.
"We need a long lefty desperately," Leyland said. "He was starting in Toledo, so he'd fit in that role."