Horford suffered the injury in the Hawks' double-overtime victory over the Cleveland Cavaliers on Thursday and was evaluated on Friday afternoon. Horford was injured with 1:35 remaining in the first overtime and didn't practice Friday, Vivlamore reports. No timetable has been placed on his return.

The Hawks' best player, Horford has averaged 18.6 points, 8.4 rebounds and 1.5 blocks for a surprising Atlanta team. In fact, Horford put up 22.6 points, 8.8 rebounds and 1.6 blocks in his last five games, including 25 points against the Cavaliers. 

At 16-13, the Hawks are in the middle of the Eastern Conference playoff race.