Horford suffered a sprained right ankle in the third quarter of Tuesday night's win at Miami. He did not practice Thursday and is listed as doubtful for the next two games, including a home game against New Orleans on Friday.
The Hawks already are without Marvin Williams, who has missed nine consecutive games with a lower back injury. Williams says he felt no discomfort in practice Thursday but he has not been cleared for any contact.
The Hawks have relied on their depth to win eight of their last 10. They trail first-place Miami by only two games in the division.
BOBCATS 100, 76ERS 97
In Charlotte, N.C., D.J. Augustin scored a career-high 31 points, including four free throws in the final 11 seconds, Gerald Henderson added three big baskets late, and the Bobcats beat Philadelphia.
Avenging an overtime defeat to the 76ers four days earlier, the Bobcats won their second straight game the same night they found out forward Tyrus Thomas would be out up two months with a knee injury.
Thaddeus Young scored 15 of his 21 points in the fourth quarter for the Sixers, who rallied from an eight-point deficit to take the lead before Henderson hit three consecutive jumpers.
Andre Iguodala added 19 points, but missed a free throw and a jumper in the final minute in Philadelphia's second straight loss.
BULLS 82, MAVERICKS 77
In Chicago, Derrick Rose scored 26 points as Chicago beat Dallas.
Rose shot 9 for 28 from the field, shouldering a larger-than-usual share of the offensive load in the absence of injured forward Carlos Boozer.
Dirk Nowitzki scored 19 points to lead Dallas, while Jason Terry, Tyson Chandler and DeShawn Stevenson added 12 points apiece.
Stevenson took all 10 of his shots from 3-point range.
After Rose's pull-up jumper gave the Bulls an 80-77 lead with 55 seconds to go, Terry missed a tying 3-pointer with 15 seconds to play. Chicago's Kyle Korver then made two free throws to seal the win.
The Mavericks were coming off a win over the Los Angeles Lakers on Wednesday night that snapped a six-game skid.