DALLAS -- Down by 13 points with less than 10 minutes remaining, youthful Oklahoma City could have easily have been content knowing they could go home for a Game 5 still needing to win only one more game.
The Thunder, with their 20-something All-Star duo Kevin Durant and Russell Westbrook, are instead going home to wait and see who they will play next.
And it was their other emerging star who led the way.
James Harden scored 15 of his 29 points in the fourth quarter, including nine in a 12-0 run, and the Thunder rallied for a 103-97 victory Saturday night to complete a first-round series sweep of the defending NBA champion Dallas Mavericks.
"I got into attack mode. I was determined to make plays," Harden said.
"He was phenomenal," said Durant, who scored 24 points. "His pick and roll game is unreal. It's fun to watch, fun to be part of. The best part about our team is that we have a lot of guys who can play off each other, and we complement each other well."
Dallas led 86-73 after Jason Terry hit a 3-pointer with 9:44 left before the Harden-fueled surge over 3 minutes when the only other score was a 3-poitner by Durant.
Oklahoma City finally took the lead, and kept it, after Westbrook stole the ball from Dirk Nowitzki and passed to Serge Ibaka for a two-handed slam that made it 92-91 with 5:17 left.
"This goes without saying, I'm excited we won the series," coach Scott Brooks said. "James had an incredible game. We ran pick and rolls at the angles. ... He was making plays for himself or our shooters."
Durant had 11 rebounds, while Westbrook and Fisher had 12 points each.
Oklahoma City plays the winner of the series between the Los Angeles Lakers and Denver. The Lakers lead that first-round series 2-1 going into Game 4 on Sunday night in Denver.
It was the first four-game postseason sweep for the Oklahoma City franchise since 1996, when they were still the Seattle SuperSonics and swept the Houston Rockets in the second round.
Dallas is the second defending champion in five years to be swept in the first round. Miami lost in four games to Chicago in 2007, after beating the Mavericks in the 2006 NBA Finals.
Dallas had never been swept in a best-of-seven series. And the Mavericks hadn't lost four playoff games in a row since 2006 against the Heat.
But now they are the oldest team in the NBA, and vastly changed from last year's championship squad.
"It was an up and down year," said Nowitzki, the 11-time All-Star who had 34 points. "We weren't consistent enough throughout to be an elite team."
Even when Harden bobbled the ball after Oklahoma City took the lead for good, Fisher ended up with it and drove for a layup to make it 96-91. Fisher, a late-season addition to the young Thunder, won five NBA titles with the Los Angeles Lakers.
Nowitzki then had a shot that hit the rim a couple of times before falling out, among several near misses for him down the stretch.
"If you want to be an elite team in this league, you got to have two or three guys who can go off at any time," Nowitzki said. "I just thought they had more weapons than us."
Oklahoma City finished off the Mavs without starting center Kendrick Perkins, who left the game with 4:09 left in the first quarter with a right hip strain. He had two rebounds, two assists and missed his only shot in his 8 minutes.
Jason Kidd, the Mavericks' 39-year-old point guard, had 16 points and eight assists. Jason Terry had 11 points in what might have also been his last game in Dallas.
After Terry's 3-pointer, Harden scored seven in a row – on a three-point play and two other baskets. Durant then made a 3-pointer. After Nowitzki was short on a 14-footer, Harden drove for a powerful two-handed slam that got the Thunder within 86-85.
"He got up a head of steam and was great," said Rick Carlisle, the Mavs coach whose four-year contract is up. "We tried everything, five or six different coverages going. We needed to be better but it was more about how good he was."
The Mavs had looked like they were ready after halftime to at least force the series back to Oklahoma City, where they opened the series with two losses by a combined four points before losing by 16 at home in Game 3.
The game was tied at halftime before Nowitzki had 12 points and Kidd made three 3-pointers in the third quarter, when the Mavs scored 34 points to take an 81-68 lead.
Nowitzki drove around Ibaka for a tiebreaking one-handed reverse layup less than a minute into the second half, and the lead was up to 64-54 when Shawn Marion had a slam.
Carlisle had talked about the Mavericks controlling their emotions after his outburst in the first quarter of Game 3. He had to be held back by an assistant coach when he charged onto the court and was pointing and screaming at an official because of what he said were three missed calls on one possession, ending with Oklahoma City scoring on what appeared to be basket interference.
Before the end of the first quarter Saturday night, Carlisle was mad again – and for good reason.
Kidd had bad pass that went out of bounds, but officials missed that the ball was deflected in the air by Harden. Replays showed clearly that Carlisle had a gripe and that the loud boos were warranted. Fisher then made a 22-foot jumper.
"Not our year. Take your hat off to them. They're a good young team," Terry said. "The balls were definitely bouncing their way. You have to give them credit. It just wasn't our time."
Notes: This was Dallas' 23rd best-of-seven playoff series. The only time the Mavericks had ever been swept in the postseason was in the a first-round series in 1990 when they lost a best-of-five against Portland. .... Ibaka fouled out with 2:14 left.