Brett Lawrie was taken out of Canada's exhibition game against the Cincinnati Reds on Wednesday with discomfort in his side.
The Toronto Blue Jays third baseman left the game in the third inning of the 12-2 loss.
Manager Ernie Whitt said he didn't know when Lawrie suffered the injury.
"He was only going to play four innings tonight anyways," said Whitt, who added they would re-evaluate Lawrie during a team workout Thursday. "We're always cautious of individuals if they feel anything. We don't want to hurt them or extend their injuries, so we just took him out."
Lawrie competed in the 2009 World Baseball Classic as a pinch-hitter, but never drew an at-bat.
Canada opens the World Baseball Classic on Friday against Italy before games against Mexico on Saturday and the United States on Sunday.