Remember when the undermanned Atlanta Hawks defeated the Boston Celtics in an NBA Cup match earlier this month?

Apparently Atlanta’s roster has raised a red flag to the NBA.

The NBA has fined the Hawks $100,000 for violating its player involvement policy in their Nov. 12 win over the Celtics at TD Garden, pointing out that star guard Trae Young was healthy enough , to play, and should not have been excluded.

“After an investigation, including review by an independent physician, the NBA concluded that the Hawks excluded Young from a game in which he could have participated in accordance with the policy’s medical standards,” the league said in a statement . “The organization’s conduct violated the policy designed to encourage participation in the NBA regular season.”

On the surface, it’s strange that the Hawks are ruling out their star player for arguably their most important game of the young season: a road game against the defending champion Celtics in their first game of the NBA Cup bracket. (The Hawks ruled Young out due to “right Achilles tendonitis,” although he had two full days off before the Nov. 12 game. It is the only game he has missed so far this season.)

However, Atlanta may have had the motivation to give Young a breather; Just eight days earlier, he played one of the worst games of his career against Boston, scoring just two points on one of 10 shots in a 30-point home loss to the Celtics.

In fact, the young-less Hawks thrived without their All-Star guard in that Nov. 12 matchup, defeating the Celtics 117-116 thanks to standout performances from Dyson Daniels and Jalen Johnson.

This decision to sit out Young will cost Atlanta, but the team now controls its own fate in the group stage of the NBA Cup; If the Hawks beat the Cleveland Cavaliers on Friday, they will win Group C and advance to the quarterfinals.

If Atlanta loses to the Cavs, Boston can win the bracket by beating the Chicago Bulls in the NBA Cup on Friday night. Celtics-Bulls tipoff is scheduled for 8:00 p.m. ET on NBC Sports Boston.