Watch the Hawks hit Onyeka Okongwu with a game-winning pick against the Celtics.

Trae Young was sidelined with right Achilles tendonitis. Bogdan Bogdanovic was ruled out due to right thigh tendinopathy.

But the Atlanta Hawks had Onyeka Okongwu, and the big man was there when they needed him most and provided the game-winning goal.

Boston had a few chances to get the win back, but had a turnover on an inbounds pass to Jayson Tatum, then Jaylen Brown missed a good look on a midrange pass and the Hawks escaped with a Boston victory.

Dyson Daniels performed on both ends of the court and scored 28 points to lead the Hawks, while veteran Larry Nance Jr. contributed 19 points off the bench for Atlanta. Okongwu finished with 15 points.

Brown was on fire for most of the game and finished with 37 points for Boston, while Derrick White had 31 points, including seven 3-pointers.

The Celtics haven’t been great lately – they have enough talent to continue winning games without Kristaps Porzingis (and Brown also missed a handful of games), but they haven’t looked like themselves. Call it a minor slump, a delayed championship hangover, or whatever you want, but this was a tough loss.

Atlanta is now 1-0 in Group C NBA Cup games. For Boston to advance from the group stage to the knockout rounds, it must beat Cleveland in a huge game next Tuesday, win 3-1 and have a chance. There are a few losses (the point difference is crucial).

To accomplish all of that, the Celtics will have to be sharper than they have been lately.