"It's not good news," Indians manager Manny Acta said. "If a guy like him comes out of a game just like that, it's not good, especially the calf."
Hannahan's departure came on the same day the Indians had shortstop Asdrubal Cabrera rejoin the lineup after missing a game with a left knee injury. Such setbacks have provided an unfortunate theme to this season for the Tribe.
In the third inning, Hannahan felt discomfort in his calf after collecting a single against Kansas City lefty Jeff Francis. Hannahan advanced to third base later in the inning, but he was replaced by pinch-runner Lonnie Chisenhall.
"I just felt some tightness and it didn't loosen up," Hannahan said. "I think I'll know more [Monday]. I felt it coming out of the box."
Asked if he had a guess as to how much time he might miss, Hannahan shrugged.
"No clue," he replied.
Cleveland lost Hannahan amid a hot streak at the plate.
Over his past 19 games, Hannahan has hit at a .381 (24-for-63) clip, giving the Indians improved offense to go along with his stellar defense. As a result, Chisenhall has been reduced to bench duty while Cleveland stayed with Hannahan's hot hand at the hot corner.
In 104 games for the Tribe this season, Hannahan is batting .248 with eight homers and 36 RBIs.
"It couldn't have come at a worse time," Acta said. "But we have to keep plugging away. It's time for Lonnie to get some more playing time and see what he can do."
Hannahan joined a list of walking wounded that also includes designated hitter Travis Hafner, second baseman Jason Kipnis, pitchers Josh Tomlin and Carlos Carrasco, and outfielders Michael Brantley, Grady Sizemore and Shin-Soo Choo. The Tribe is hoping to have Sizemore and Kipnis back from the disabled list some time during the coming week.
Jordan Bastian is a reporter for MLB.com. Read his blog, Major League Bastian, and follow him on Twitter @MLBastian. This story was not subject to the approval of Major League Baseball or its clubs.