Troy Tulowitzki injured his ribs trying to stop a single during the eighth inning against the Nationals on Thursday night.
An MRI of Tulowitzki's right side revealed a broken rib, which could sideline the shortstop for four to six weeks.
"I'm just really upset. I worked so hard (to get back)," Tulowitzki said. "I'm in a lot of pain right now; I'm not sure how long (I'll be out).
"It's just an unfortunate thing that happened. I will be back and be even better." Tulowitzki ranks in the top five in the National League in batting (.347 average), on-base percentage (.413), home runs (16) and RBIs (51) and has been nearly flawless in the field.