Jimmy Butler admitted the Miami Heat will have to improve markedly when they face either the Toronto Raptors or the Chicago Bulls in the Eastern Conference eighth-seed game on Friday in the NBA play-in tournament.

The Heat were beaten 116-105 by the Atlanta Hawks in the seventh seed clash on Tuesday at Kaseya Center.

A slow start from Miami saw them trail by 15 points at half-time, and they were unable to make up that deficit in the second as Atlanta eased to victory to book their place in the playoffs.

Butler scored 21 points with nine assists, but just four rebounds, and he lamented his and his teammates' inability to retrieve the ball all game, with the Hawks making 63 overall to the Heat's 39.

"We have to stay confident," Butler said. "We have to know we are capable of winning, if we start out the right way and if we rebound, obviously.

"But it's just, I don't know, shots don't go in, we foul, that's never the recipe for success with us. So come Friday, we've got to play legit the exact opposite that we played tonight.

"Rebounding was just horrendous. We didn't put body on body and they got all the rebounds, all the second-chance points. And that was the game."

Heat coach Erik Spoelstra concurred, adding: "There's probably been a little bit more than a half-dozen times, maybe eight to 10 times, where we have not rebounded where it has just been absolutely crippling, in terms of how it's hurt us.

"We definitely have to get to the film and go back to all the fundamentals. We knew coming into this game, this game would be decided [by] ball in the air, ball on the floor, and it certainly was."

Hawks center Clint Capela made an impressive 21 rebounds in the game, and Heat guard Tyler Herro – who scored 26 points – thought bad luck came into play, but admitted that could not be used as an excuse.

"The ball was bouncing their way, literally, the whole game," Herro said. "But that's not any type of excuse to why we couldn't rebound the ball.

"They beat the hell out of us on the glass, so it wasn't even close. So we can point fingers, do whatever, at the end of the day they beat the hell out of us on the boards and that's what it is."

Trae Young starred for the Hawks, scoring 25 points with seven assists and eight rebounds, and he anticipates a tough encounter with the second seed Boston Celtics in the first round of the playoffs.

"Obviously, Boston is a really good team," Young said. "But I haven't really looked too far ahead. I mean, obviously I watched them all year. They've been playing really well. But I was really focused on tonight and making sure we won."

Young also referenced Butler's comments from earlier in the week when he said he thought the Heat would get the win, adding: "I know Jimmy guaranteed a dub, so I was really focused on making sure that didn't happen."

Butler praised Young after the game, saying: "He's a hell of a player. He makes all the right reads. Obviously, he's a big time shot-maker, and he even got eight rebounds, so I don't think we took too much away [from] them tonight."