On Friday, Celtics coach Brad Stevens said Horford had done more job and has been being appraised daily. He had been held out of a reduction.
Boston, which has dropped three in a row, fought without Horford, Aron Baynes and Marcus Morris on Friday. The loss motivated a staff meeting subsequently that kept the locker room closed for more than a half an hour before eventually being opened to colleagues.
The team can be in the midst of a challenging stretch, with five consecutive matches coming against teams using .500 or better records to finish 2018.
Horford, who’s in his 12th NBA season, is averaging 12.4 points, 6.4 rebounds, 3.4 assists and also a career-high 1.7 cubes in 22 matches to the Celtics this season.
Morris, meanwhile, was also listed as questionable for Sunday’s match with right knee soreness. Baynes remains out for several weeks after breaking a bone in his hand at Wednesday’s home loss to the Phoenix Suns.