Watch: Onyeka Okongwu's game-winning tip-in shocks Celtics in Emirates Cup opener

Onyeka Okongwu tipped in a Dyson Daniels miss with 6.1 seconds for the game-winning basket in Atlanta's 117-116 win over Boston. The two teams traded turnovers before Jaylen Brown's 13-footer at the buzzer missed and let the Hawks pull off the huge upset.

The Hawks were 15-point underdogs against the defending champions, thanks to an injury report almost as long as Okongwu's 7-foot-2 wingspan. Atlanta was missing All-Star Trae Young, starter De'Andre Hunter, sixth man Bogdan Bogdanovic and the first three point guards on their depth chart.

But the Hawks got a career-high 28 points from the 21-year-old Daniels, who also had six steals in the win.

Atlanta also got the second career triple-double from Jalen Johnson and a career-high five three-pointers from Larry Nance Jr. to stun the Celtics, who led by as many as 15 points in the third quarter.

It's possible that the format of the Emirates Cup, which uses point differential as a tiebreaker, hurt the Celtics. With the Celtics perhaps prepared to run up the score, the Hawks racked up six steals in the third — part of Boston's 20 turnovers for the game.

Now the Hawks are in first place in East Group C of the Emirates Cup standings. The Celtics are still the clear NBA title favorites, but they've got an uphill battle ahead in the in-season tournament.