Eckstein sustained the injury while running the bases in Tuesday night's game against the Atlanta Braves.
It is Eckstein's second injury to his right calf this season. He is hitting .279 with one homer and 22 RBIs.
Outfielder Will Venable was activated from the 15-day disabled list. Venable, hitting .238 with eight home runs and 32 RBIs, is returning from a lower back strain.