The A's recalled infielder Andy Parrino from Triple-A Sacramento on Saturday to fill in for Callaspo.
Callaspo grabbed his leg and pulled up limping just before crossing first base during the second inning of Oakland's loss at Seattle on Friday. He exited the game and was replaced in the lineup by Nate Freiman.
Callaspo is hitting .234 with three home runs and 31 RBI in 83 games.
''To the point where we felt like it would be at least seven days before he'd be able to do anything,'' A's manager Bob Melvin said. ''Then get him out doing some baseball activity and do the best you can to try to get him back before the 15-day period. But it all starts with a week's worth of rest.''
Parrino will make his second appearance with the A's this season. He started two games for the club as a callup in mid-June.