Horford won't start Friday's game against the Spurs, Anthony Slater of ESPN.com reports.
Horford drew his first start of the season in Wednesday's loss to Houston, though he'll return to the second unit Friday. The veteran center has averaged 5.4 points, 3.8 rebounds, 2.6 assists and 1.2 blocks in 17.0 minutes per game across his last five appearances off the bench.