Replays showed Robertson reaching for his left side after inducing a popout from Minnesota's Mike Lamb to lead off the seventh inning. He threw a first-pitch ball to Matt Tolbert, before head athletic trainer Kevin Rand approached the mound along with manager Jim Leyland.
Upon examination, Robertson left the game without throwing any warmup pitches. Aquilino Lopez, who replaced an injured Dontrelle Willis last Friday at Chicago, entered the game and finished out the inning.
Robertson is expected to be fine for his next turn in the rotation on Sunday at Toronto.
The Tigers are already short one starter with Willis on the disabled list with a hyperextended right knee. Armando Galarraga is scheduled to be recalled from Triple-A Toledo to take Willis' spot in Wednesday's game at Cleveland, but the club wanted to wait until after Tuesday's game to make the move in order to keep an extra reliever for as long as they could.
Robertson allowed four runs on six hits in 6 1/3 innings, walking one and striking out five. He has proven to be one of Detroit's more durable starters over his five-year career. He missed close to a month last season with a tired arm and ended up with 177 2/3 innings over 30 starts, breaking a streak of three years with at least 196 innings.
Jason Beck is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.