TORONTO -- Minnesota first baseman Justin Morneau is day to day with a "mild concussion" after he was accidentally kneed in the head Wednesday, Twins manager Ron Gardenhire said.
Morneau is second in the AL with a .345 average, seventh in home runs with 18 and 10th in RBIs with 56. He leads the AL in on base percentage (.437) and is second in slugging percentage (.618).
Morneau was hurt in the eighth inning of Wednesday's 6-5 loss when he slid into Toronto's John McDonald while trying to break up a double play. He walked off the field without assistance but did not return.
Michael Cuddyer started at first base Thursday, and Gardenhire said Morneau could play Friday when the third-place Twins open a three-game series at first-place Detroit.
Earlier this week, Morneau won a tight fan vote over Miguel Cabrera of the Tigers and Mark Teixeira of the New York Yankees, earning his first starting nod in four selections to the July 13 All-Star Game in Anaheim.
Morneau went on the disabled list in April 2005 after he was hit in the head by a pitch from Seattle's Ron Villone, suffering headaches for several days and missing 13 games. He also sustained head injuries during his days as a youth hockey goaltender and high school basketball player in Canada.
"He doesn't feel very good," Gardenhire said. "We'll see how he is tomorrow. It knocked him a little loopy, as a Canuck goes."
Morneau was examined by doctors following Wednesday's game and was in uniform Thursday, with Gardenhire not ruling out using him as a pinch-hitter.