"I'd like to be able to explain exactly what happened," Reds manager Bryan Price said. "I thought he tripped and did something when he went down. I think it happened after he bunted the ball and was leaving the box."
Bourgeois laid on the ground for several moments and was tagged out by third baseman Trevor Story.
"That was going to be a bunt base hit," Price said. "He actually got the bunt down and was in good shape when he was leaving the box and something happened. He wasn't in the position to tell me what happened at that time. We'll probably know more [Sunday] morning."
Bourgeois left the field with head trainer Paul Lessard to undergo tests. He is competing for a spot on the Reds bench this spring as an extra outfielder.
In eight games, Bourgeois is batting .350 (7-for-20) with one home run.
Mark Sheldon is a reporter for MLB.com. Read his blog, Mark My Word, and follow him on Twitter @m_sheldon. This story was not subject to the approval of Major League Baseball or its clubs.