A late-developing illness prevented Jayson Tatum from taking the floor Monday night in Orlando.

The Celtics added Tatum to their injury report minutes before their road matchup with the Magic, listing the superstar as questionable with a non-COVID illness.

Al Horford replaced Tatum in the starting lineup. Tatum was not on the bench for tipoff, but Boston had not officially ruled him out as the game began.

That finally happened at halftime, with the Celtics announcing Tatum would not return. Boston led 58-43 at the time after a stellar 19-point first half from Jaylen Brown.

Tatum was coming off one of the best performances by any NBA player this season: a 43-point, 16-rebound, 10-assist tour de force in a 123-98 win over the Chicago Bulls on Saturday. He had started all but two of the Celtics’ first 28 games and entered Monday as the team leader in points, rebounds, assists and steals per game.

Before Tatum’s last-minute downgrade, the Celtics were set to have their full roster available for just the second time this season. Rotation wing Sam Hauser returned to action after missing the previous two games with lower back spasms.

The Magic were shorthanded, playing without injured stars Paolo Banchero and Franz Wagner and bench players Moritz Wagner and Gary Harris. Moritz Wagner, a candidate for NBA Sixth Man of the Year, tore his ACL on Saturday during a win over Miami.