Millsap steals Russell's Thunder
Jerami Grant scored a season-high 15 points, and Andre Roberson matched his season high with 14 points for the Thunder.
Westbrook scored 18 points in the second quarter to help the Thunder lead 53-48.
The Hawks shot 50 percent in the first half, but without Howard they were outrebounded 27-14, and OKC outscored them 10-0 on second-chance points.
Schroder scored 18 points in the first half, and Millsap added 16.
The Hawks took an 81-78 lead into the fourth, then held on.
"They made some tough plays toward the end of the game," said Thunder guard Semaj Christon.
"We can do better on defense keeping the guys in front of us without fouling."
Roberson scored his 14 on 5-for-14 shooting. He took five more shots than he had ever taken in a regular-season game.
"I'm just letting it fly, to be honest," he said.
"It wasn't falling for me early, but I stuck with it, and the team needed me to keep shooting, so that's what I was doing. I just go out there and do anything I can."
Kyle Korver heaped praise on teammate Roberson.
"Andre's just so tough. He's tough mentally and tough physically, and he has been doing that for this team for a lot of years," he said. "He never seems to get flustered out there."
Tip-ins
Hawks: Mike Muscala tipped the ball into his own basket while trying to grab a rebound in the first quarter. The basket was credited to Oklahoma City's Enes Kanter ... Ex-Thunder forward Thabo Sefolosha scored 15.
Thunder: Shot just 27.3 percent in the first quarter ... Made three of 19 3-pointers in the first half... Victor Oladipo missed his fourth straight game with a bruised right wrist ... Adams' streak of six straight games with double figures ended as he finished with six points ... Oklahoma's City's four starters other than Westbrook made seven of 26 shots and scored 24.
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