Outfielder Chris Heisey was optioned to Triple-A Oklahoma City before Saturday night's game.
Grandal was batting .400 this month with three homers, four doubles and 15 RBIs in 16 games. Among National League catchers, he was among the leaders in batting average, on-base percentage and slugging percentage.
He sustained a mild concussion against the Padres on May 22.
Heisey was batting .111 with one hit in nine at-bats.