Dallas, TX – Russell Westbrook finished with 33 points, 86 victory over the Mavericks in a battle of Western Conference contenders.
Dirk Nowitzki shot just 2-for-15 from the field and posted eight points and eight rebounds in the loss, Dallas' second over the last eight games.
Dallas shot 3-of-19 in the third quarter and watched a three-point halftime lead turn into a five-point deficit, 71-66, entering the fourth.
The Thunder led by as many as 10 in the final frame, but held just a two-point lead, 81-79, after Marion tipped in a Rodrigue Beaubois miss with 4:18 remaining.
Marion tied it at 85-all on a running hook shot in the lane with 2:14 showing, but Oklahoma City scored the next seven points to pull away.
Westbrook broke the tie with a pull-up jumper, Durant hit a turnaround the next time down and Westbrook drained a three-pointer over Marion for a 92-85 cushion with 35.9 seconds remaining.
Dallas, which led 29-21 after the first quarter and 52-49 at the break, missed three shots and had two turnovers over the last two minutes.
The Thunder lead the season series, 2-1, and host the finale on March 5...James Harden posted 10 points and a game-high nine assists for the Thunder, who owned a 55-44 advantage on the glass.