Simmons slid headfirst into first base on his game-ending groundout to shortstop in Saturday night's 3-1 loss to the Giants. National outfielder Bryce Harper suffered a torn ligament in his left thumb when he slid into a base headfirst on April 25.
Harper will be out until at least early July after undergoing surgery on April 29.
Simmons played in 157 games last year and has only missed two this year when he sat out from April 10-11 after jamming his right wrist during a home-plate collision with Mets catcher Travis d'Arnaud on April 9 at Turner Field.
Mark Bowman is a reporter for MLB.com. Joe Morgan is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.