"I just started my swing and just tried to stop and pull back and put the brakes on," Story said.
Story is eligible to be activated next Saturday in Cincinnati, though it's unclear when he will return to baseball activity. He will undergo regular treatment and strengthening exercises in the meantime.
Story missed the final two months of last season after undergoing surgery on a torn ulnar collateral ligament in his left thumb, suffered when sliding into second base and then falling on it when diving for a ground ball on July 30 against the Mets.
At the time of his injury, Story led the National League with 27 homers, a rookie record for a shortstop, and the Rockies were four games back of the second NL Wild Card, though they eventually finished 12 games under .