Boston Celtics rookie Baylor Scheierman has been added to the injury report with a fractured left thumb, casting doubt on his availability for Sunday’s prime-time matchup against the Philadelphia 76ers, according to the team’s Saturday injury report.

Scheierman is listed as questionable for the game after suffering the injury during a collision in transition in the first half of Boston’s recent game against Brooklyn, according to team reports. The rookie was seen grabbing at his thumb following the incident and went to the bench to have it taped before returning to finish the game.

The fracture affects Scheierman’s shooting hand, which complicates his ability to play through the injury. While players can sometimes continue playing with non-displaced fractures on fingers or thumbs, the location on his dominant hand presents additional challenges for the young guard.

The Celtics have not provided details on exactly how the injury occurred. Team medical staff are reportedly working on possible tape configurations to protect the thumb if Scheierman attempts to play through the fracture without further aggravating the injury.

With only seven weeks remaining in the regular season, the timing of the injury raises concerns about Scheierman’s availability for the remainder of the campaign. If he requires the typical healing time for a bone fracture, he could miss most or all of the remaining games, though the team has not indicated any long-term timeline.

Scheierman has emerged as a key contributor during Boston’s recent defensive improvements. He has been effective in one-on-one defensive matchups and is grabbing more than 20 percent of available defensive rebounds, according to team statistics.

“His rebounding outside of his area is big,” Celtics head coach Joe Mazzulla said recently. “So whether he’s boxing the guy out or whether he’s on the perimeter, he comes back and crashes defensively and gets those, and so that helps us get out in transition, but I think he’s playing at a great level for us defensively, and really on the rebounding piece on both ends.”

The rookie’s production has increased significantly in February, when he has started nine of 11 games. During the month, Scheierman is averaging 7.7 points, 6.5 rebounds, and 2.4 assists per game, according to team statistics. Those numbers represent a substantial improvement over his season averages of 4.2 points, 3.0 rebounds, and 1.1 assists.

The injury report also confirmed that star forward Jayson Tatum remains out for Sunday’s game despite speculation that NBC’s decision to move the Celtics-Sixers matchup to prime time indicated his potential return. Celtics fans had been monitoring the injury report for any upgrade in Tatum’s status from out to doubtful or questionable, which typically signals an impending return to action.

Sunday’s game against Philadelphia will test Boston’s depth as they potentially face the 76ers without both Tatum and possibly Scheierman. The rookie’s absence would be particularly notable given his recent strong play and increasing role in the rotation.

The Celtics will likely provide more information about Scheierman’s status and treatment plan in the coming days as they determine whether he can safely play through the fracture or if rest is necessary for proper healing.