Calhoun led off the inning and hit a grounder to second base. He caught his right foot on a soft spot just beyond the base and needed to be helped off the field.
"I just rolled it and it hurt real bad," said Calhoun, who was on crutches after the game. "It's just a freak thing, you know?"
The 26-year-old, who is in his third big league season but first as a full-time starter, is a .266 hitter with 11 home runs and 39 RBIs in 93 career games. But he was heating up of late: Calhoun is 7-for-15 with three doubles, a triple, a home run and six runs in his last three games.