Bour appeared to injure it while planting his left foot on the bag on a bang-bang play with Chase d'Arnaud. While the play was under replay review, Bour tried to walk off the discomfort.
"I was just planting, stepping on first, [and] my right foot got caught," Bour said. "Rolled my ankle. It'll just be a day to day kind of thing, keep the inflammation down. We'll know tomorrow."
The sixth inning opened with d'Arnaud's roller to first. Pitcher Jose Fernandez dashed to first, but Bour elected to take it himself and was shaken up. After a review of one minute and 59 seconds, the out call stood.
"I just thought it would be better if I made the play," Bour said on why he didn't flip to Fernandez. "Just got messed up on the footing."
Bour remained on the field, but he was then lifted for Chris Johnson.
"At one point, I just realized I couldn't make a play if there was a ball to me," Bour said. "Once you're in a situation where you can't help the team, you've got to come out of the game."
Bour, batting .268/.347/.526, is Miami's primary left-handed power threat with 15 home runs and 46 RBIs.
Manager Don Mattingly said the ailment is more lower leg than ankle. But either way, Bour will receive treatment and see how it responds. The injury doesn't appear serious.
"I've had rolled ankles before," Bour said. "It just got to a point where I couldn't do it anymore."
Joe Frisaro has covered the Marlins for MLB.com since 2002. He writes a blog, called The Fish Pond. Follow him on Twitter @JoeFrisaro and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.