Ramirez has struggled at the plate this season and has been bothered by a bruised left thumb for some time. The 31-year-old is hitting only .168 through 47 games this season, with five home runs and 22 RBI.
To take his place on the roster, the team recalled infielder Chad Tracy from Triple-A Iowa.
Tracy, 30, spent 19 games with the big club earlier in the season. He is hitting .396 with five homers and 18 RBIs in 26 games for the Iowa Cubs -- going 4-for-4 Tuesday and 7-of-13 at the plate before his call-up.