Marcus Morris took Horford's spot in the lineup, making his first start since last season. Morris had 8 points and 4 rebounds in 24 minutes.
Horford was listed as probable with the same injury before Wednesday's home loss to the New York Knicks but finished with 19 points, 7 rebounds and 5 assists in 35 minutes. Coach Brad Stevens decided to rest him after Friday's shootaround.
Horford is averaging 11.7 points, 6.3 rebounds and 3.6 assists in his third season with the Celtics. The 12-year veteran spent his first nine seasons in Atlanta.
Morris is averaging 13.9 points and 6.6 rebounds in 17 games.
Information from The Associated Press was used in this report.