DALLAS -- The Dallas Mavericks went into Saturday night playing for pride.
Oklahoma City beat the defending NBA champions at that, too.
Rallying behind James Harden and Kevin Durant, the Thunder stormed back from 13 points down in the fourth quarter to end Dallas' title reign in a stunning 103-97 fashion at American Airlines Center.
"We took it one possession at a time," Durant said. "The Mavericks went on a nice little run in that third quarter, and we didn't crumble. I think that's part of our team. We're growing in that area and we never gave up, and we kept fighting."
Oklahoma City advances to the Western Conference semifinals after dispatching the Mavericks in just four games. Dallas, a franchise that had never been swept in a best-of-seven series, failed to win one game in defense of its first NBA championship.
"They're a great young team," Mavericks coach Rick Carlisle said. "And the thing that impressed me the most about them is that they have a certain look in their eye right now. Not just that they belong, but that this could be their time."
A steady dose of Harden kept the Thunder within striking distance before Durant awoke from a three-quarter slumber. Durant's 3-pointer with 7 1/2 minutes left cut the Dallas lead to 86-83 and prompted a quick timeout from Carlisle.
It didn't help.
After Dirk Nowitzki missed a contested fall-away, Harden blew past Jason Terry for a two-handed slam. Another trey from Durant tied the game at 88 with six minutes left.
Serge Ibaka gave the Thunder the lead for good with 5:16 remaining. Harden scored 15 of his 29 points in the fourth. Durant had nine of his 24 in the final period. Russell Westbrook's defense locked down surprise Dallas starter Jason Terry.
"We were down. That third quarter, I didn't like the fact that they came out and they really got into us," Thunder coach Scott Brooks said. "They really dictated the game. We were on our heels and trying to run our offense from spots we don't need to be or run our offense through.
"We were down 13 and a lot of things did not go our way because of us, and because they were making big plays. But we kind of changed that around by really getting into the basket."
Harden iced the win by blowing by Jason Kidd for a layup with 10 seconds left.
"Scotty put the ball in my hands in the fourth quarter, and he told me to make plays," said Harden, who added five assists. "So, I was just trying to make plays. And Russell did a great job on the defensive end with a couple of steals in a row, and chasing Jason Terry. It was just tremendous."
Nowitzki, the Finals MVP last June, fought through constant physical double-teams to pace the Mavericks with 34 points. Kidd added 16. Jason Terry, who started a playoff game for the first time since 2009, had 11.
Dallas eliminated the Thunder in five games in the West finals last year. This OKC team wasn't the same squad.
"They came at us like a buzz saw in the fourth quarter," Carlisle said. "They made plays, we couldn't stop them, and they were able to stop us enough. We walk away from this very disappointed, but knowing that the better team won."
The Mavericks emerged from halftime looking like the team that made an improbable run to a title less than a year ago. The offense was flowing through Nowitzki, whose shots finally started finding the bottom of the net with regularity.
The young and athletic Thunder appeared a half-step too slow as the Mavericks zipped the ball to open shooters. Two nights ago, Oklahoma City was putting the game away in the third quarter.
In this third, OKC found itself playing from double-digits down.
Kidd drilled two 3-pointers in the third, and the Mavericks hit five from downtown. Dallas went into the final 12 minutes up 13 (81-68) and seemingly in control.
Oklahoma City was on top for most of the first half but couldn't shake the Mavericks. Dallas jumped ahead briefly late in the second period thanks to an 8-0 run.
Shawn Marion ignited a sequence that began by stuffing a Russell Westbrook jumper and ended with an Ian Mahinmi lay-in. Dallas was up 38-37 and the teams traded baskets for the rest of the period.
The game was tied 47-47 at the half. That had to feel like a lead for a Mavericks team on the brink of elimination.
The Thunder's two All-Stars -- Durant and Westbrook -- didn't have much of the imprint on the proceedings before the break. Nowitzki heated up late in the second quarter to pace Dallas with 13 points.
Oklahoma City did take the early edge to start the night. Thunder off guard Thabo Sefolosha knocked down a couple of shots, including a 3-pointer and a jumper for a 7-2 advantage in the first two minutes.
On the Mavericks' first possession, Nowitzki was met at the rim by Ibaka and the ball went the other way. Ibaka wagged his finger, channeling Dikembe Mutombo.
The Mavericks, though, didn't crumble as they had in Game 3. Kidd, finding a jumper that hasn't been there, scored seven points in the first seven minutes.
His 3-pointer gave Dallas a 15-14 lead, the first edge for the Mavericks in their building. And it was the first time since the series shifted from Oklahoma City that the Mavs showed some fight.
The Thunder took a 26-24 lead into the second quarter, with Harden scoring seven.
NOTES: Carlisle started Terry for the first time in the series, replacing Delonte West. Terry, a soon-to-be free agent, acknowledged his career in Dallas is likely over after the playoffs. ... The Mavs became the 100th team to lose after trailing a best-of-seven series 3-0. ... The Oklahoma City franchise has just one previous sweep in its history, but that came when it was the Seattle SuperSonics. The Sonics swept the Rockets 4-0 in the West semifinals in 1996.