CLEVELAND -- Kyrie Irving gave the Cleveland Cavaliers some much-needed good news Wednesday night.

Irving scored 18 of his 33 points in the third quarter, and the injury-riddled Cavaliers beat the Atlanta Hawks 99-83 -- Cleveland's largest margin of victory this season.

Irving's big night came at a perfect time for his team, which hasn't had much to feel good about lately. The Cavaliers lost 5-of-6 overall and six straight at home going into the game, but that seemed minor compared to the news that came earlier in the day.

Center Anderson Varejao will have surgery Thursday to repair a muscle that split near his right knee. He will miss six to eight weeks. Varejao was having an All-Star-caliber season, averaging 14.1 points and an NBA-leading 14.4 rebounds. Irving admitted the Cavaliers, who had only 10 available players, were thinking about their sidelined teammate throughout the night.

"Andy's production, his effort, his whole morale around the team will be missed," Irving said. "We all have to step up."

Added coach Byron Scott: "The biggest thing we talked about before the game was having fun. Let's see what happens. Play hard, play together and play smart. We did all three of those things."

Josh Smith scored 17 points to lead Atlanta, which has lost a season-worst four straight. Hawks coach Larry Drew, who called his team "soft" following Tuesday night's loss to Minnesota, watched them get completely outplayed after tying the game early in the third. His mood wasn't any better following the latest lackluster effort.

"I am a little concerned right now," Drew said. "I've got to do something to get this team on stride again -- and I will."

"The energy and the effort isn't all there right now," center Al Horford said. "It's about energy, man, and we need to defend better."

Alonzo Gee scored 15 points for Cleveland, while Tristan Thompson added 11 points and 14 rebounds. Rookie Tyler Zeller, who moved into the starting lineup after Varejao was injured Dec. 18, scored 11 points and had a career-high 12 rebounds.

Jeff Teague added 15 points for Atlanta, and Horford scored 14.

Atlanta's frustration was best summed up when Smith shot an airball from the free throw line midway through the fourth quarter with the Hawks trailing 88-76. With the crowd jeering, he also missed the second shot and the Hawks slowly went up the court to play defense. Atlanta tied a franchise low by attempting five free throws. The Hawks made two, a league low for the season.

C.J. Miles (back spasms), Daniel Gibson (concussion) and Luke Walton (personal matter) also missed the game for Cleveland.

Hawks point guard Devin Harris played for the first time since Dec. 18 after missing 11 games because of a sore left foot. Guards Anthony Morrow (strained right hip) and DeShawn Stevenson (sore knee) didn't play.

Cleveland, which hit seven 3-pointers in the opening quarter, led for most of the first half. Atlanta tied the game at 51 early in the third quarter, but the Cavaliers surged ahead thanks mostly to Irving, who dazzled the Hawks with jump shots and drives to the basket that resulted in free throws. He also hit two 3-pointers, including one from a couple of feet behind the arc with 1.9 seconds remaining to give Cleveland a 77-63 lead.

Drew, who criticized his team's effort following a 108-103 loss to the Timberwolves, didn't back down from the words before playing the Cavaliers, saying he emphasized his point in a breakfast meeting with his players Wednesday.

"Things aren't going too good for us right now," Smith said. "You're going to have struggles like this throughout the season. We've got to get back to playing beautiful basketball."

The Hawks had won eight of nine over the Cavaliers. Atlanta has lost four in a row for the first time since closing the 2010-11 season on a six-game slide.

Varejao's injury was originally diagnosed as a bruised right knee, but he still wasn't ready to practice. He will have surgery on Thursday at The Cleveland Clinic. The team said Dr. Richard Steadman in Vail, Colo., provided a second opinion on the injury.

Game notes
The Hawks are 7-3 in the second leg of back-to-back games. ... Harris, who went into the game averaging 7.7 points, was scoreless in 13 minutes. ... Atlanta hosts Utah on Friday night. ... Cleveland begins a five-game road trip in Denver on Friday night. ... Gibson has missed the last six games. He was injured against the Hawks after a collision with Morrow.