Simmons sustained the injury while sliding into second base during the fifth inning of Sunday's game against the Phillies. While he'll be evaluated further on Monday, the initial diagnosis almost certainly means a trip to the disabled list, possibly for more than the minimum 15 days. Should that be the case, the Braves will be able to date the move back a few days because of the All-Star break, but this is significant loss under any circumstances.
On the season, the 22-year-old Simmons, who's likely a future Gold Glover at the position, is hitting .292/.333/.442 in 123 plate appearances. Simmons was called up in early June to take the place of the struggling Tyler Pastornicky, the Braves' other rookie shortstop.