The timing of his removal was funny, because Ellsbury would initially stay in the game, gather an infield single, steal second base and then score from second on a single. That doesn't sound like the activity of a man with a foot injury, but he was removed before the eighth inning.
The game was tied at the time, too, so it's not like they had a big lead and were deciding to rest him.
At the end of the day, however, the likelihood of a serious injury seems relatively low, considering his wheels after the foul ball.
Ellsbury, 29, is hitting .298/.356/.421 with 29 doubles, eight triples, seven homers, 83 runs scored and 49 stolen bases in 53 attempts this season.