Vladimir Guerrero Jr. was a late scratch from the Toronto Blue Jays' lineup Wednesday night against the New York Yankees because of right knee discomfort.
Guerrero had an MRI during the game, and the team expects to know more Thursday.
"He didn't feel quite right, his pregame hitting routine," manager John Schneider said after Toronto's 6-1 victory. "Just obviously want to be careful with him. So didn't want to push it today."
The slugger had been slated to bat third as the designated hitter for the Blue Jays, who are in a tight playoff race. Toronto remained a game ahead of Texas and Seattle for the second of three American League wild-card spots.
About two hours before Wednesday night's game, Schneider said Guerrero's sore right knee has been "barking" for a couple of days and he's been "grinding" through it, but there's nothing structurally wrong.
Approximately 40 minutes before the scheduled first pitch, however, the Blue Jays announced Guerrero had been removed from the starting lineup.
Toronto rookie Spencer Horwitz was shifted from first base to DH. Cavan Biggio moved from second base to first and was bumped up a slot in the batting order to third. Whit Merrifield was inserted at second base, hitting sixth.
Guerrero went 0-for-5 on Tuesday night in a 7-1 victory at Yankee Stadium and was lifted for a pinch-runner in the ninth inning after reaching on an error.
The Associated Press contributed to this report.