Atlanta's Tim Hardaway Jr. scored 22 points as the Hawks stunned the NBA champion Cleveland Cavaliers 114-100 on Friday despite sitting their starters.
The Hawks didn't use any of their five starters against LeBron James's Cavaliers who had their four game win streak snapped.
James finished with 27 points but it wasn't enough for the Cavaliers as Mike Dunleavy came off the Atlanta bench to score 20 points and the depleted Hawks had a half dozen players in double figures.
"Obviously a bad performance," Cavs coach Tyronn Lue said. "There's really no other explanation."
Paul Millsap, Kent Bazemore, Dwight Howard and Dennis Schroder all sat out for rest after a 123-116 win over the Boston Celtics on Thursday.
Thabo Sefolosha (right groin strain) has been out and Atlanta didn't want to play Millsap or Bazemore on consecutive nights after recent injury woes.
The win vaulted Atlanta past the Milwaukee Bucks for fifth spot in the Eastern Conference standings.
James also had eight rebounds and seven assists for the Cavs, whose lead over the Boston Celtics for first place in the East is now at one game with three to play.
Kyrie Irving added 18 points and Kevin Love contributed 15 points and 15 rebounds, but the Cavs made just nine of 36 three-point attempts, and trailed by 20 points with just under two minutes remaining.
Irving left the game in the third quarter and went to the locker room because of soreness in his surgically repaired left knee.
He returned in the fourth quarter, but took just one shot in the final period.
"Just after halftime my left knee just started kind of flaring up," Irving said. "Yesterday just was a terrible day for me and my knee. But I did everything possible just to recover and just come in today and felt good. And then after halftime just coming in and sitting down for 15 minutes and trying to get back going, started feeling it. But I'll be all right."
The two teams play again on Sunday in Atlanta.
"It was a great feeling but we have to do it again on Sunday," Hardaway said. "We're not going to be happy about this. We know we have to see them on Sunday. They're going to come after us."
Lue certainly hopes they do. He was left shaking his head two days after his team's thorough 114-91 victory over the Celtics in a battle for the Eastern Conference lead.
"To beat Boston and have the game that we had and to come back and not validate it against a team that didn't even play their guys," Lue said. "I didn't think we respected them tonight. I thought we thought we'd just mess around with the game until it was time to knuckle down.
"By that time they already had confidence. That's who we've been. That's who we are. I hate it."