The Thunder needed 25 points from Kevin Durant, including 11 in the fourth quarter, to hold off a short-handed, but inspired Magic team 97-89 on Friday night.
"That's what we have to hang our hat on is making plays on the defensive end," Durant said of Oklahoma City's late-game effort, which included holding Orlando without a field goal in the final 2:26. "We made big plays when we needed them."
Russell Westbrook added 19 points and Oklahoma City ended a two-game losing skid despite going just 5 for 21 from the 3-point line.
They entered the night trailing West-leading San Antonio by 2½ games.
"We had two tough losses ... I give our guys a lot of credit," Thunder coach Scott Brooks said. "They picked themselves up and came into tonight with a good mindset. We got the win and we're moving on to the next game."
The Magic briefly took a one-point lead in the final period, but the Thunder hit eight of their final 10 free throws to help seal the victory.
Orlando lost its sixth straight. They also lost starting shooting guard Arron Afflalo in the second quarter with a right hamstring injury.
"The first half, I think I was a completely different player in the first half than in the second half," said Harkless. "The first half I wasn't aggressive. ... When Arron went down I knew I had to step up and make plays, make things happen."
For a while it looked like Harkless might propel to the Magic to the upset.
After a sluggish first half, Orlando took its first lead since early in the first half, 78-76, on a jumper by Beno Udrih with 7:29 to play in the game.
The Thunder fought back and were leading by a point when Durant blocked a layup attempt by Tobias Harris and knocked down a 3-pointer on the other end to push their lead to 86-82.
Udrih hit a 3 to cut the deficit to a point again and following Kendrick Perkins' missed jumper the Magic tied it again on a free-throw by rookie Kyle O'Quinn.
The Thunder got blocks on Magic layup attempts on back-to-back possessions and broke the stalemate when Durant's 3 from the wing made it 89-86.
O'Quinn responded with a layup, but Durant hit 1 of 2 free-throws a few possessions later to give the Thunder a two-point cushion.
The Magic came up empty on their ensuing touch and Durant connected on a pair from the foul line to make it 92-88 with 39.1 seconds remaining.
Orlando turned it over out of a timeout, and the Thunder to closed things out at the free throw line.
O'Quinn made his first career start in place of center Nikola Vucevic, who missed his second consecutive game with what Magic coach Jacque Vaughn said was a mild concussion.
Vucevic was injured during Orlando's loss Tuesday night at Indiana.
The Magic didn't get far into the game before losing Afflalo a few minutes into the second quarter.
Afflalo was hurt while chasing a loose ball and needed assistance from teammates walking off the floor. He did not return.
Oklahoma took advantage, leading by as many as 15 points in the first half by exploiting Orlando's lack of depth in the front court. The Magic were forced to go small at times, leading to several defensive breakdowns and layups for Oklahoma City.
Despite the loss, Vaughn said he likes how his young team is closing the year.
"It's just an unbelievable overall effort from every guy," Vaughn said. "As a coach you want to be proud of your team and what they're doing. Tonight's effort typifies who we want to be."
The Thunder improved to 15-4 in games played after a loss this season. ... With O'Quinn's start on Friday the Magic now have had 22 different starting lineups this season. "How many stages are in the Tour de France?" Vaughn said when asked about the latest incarnation of his lineup. "I'm trying to get there."... Before his concussion, Vucevic had started the first 68 games of the season and was the last Magic player to miss a start. Vaughn said his return is to be determined as he goes through the league's new concussion protocol. ... PGA golfer Bubba Watson, who is competing at this week's Arnold Palmer Invitational, was in attendance.
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