Dirk Nowitzki and Shawn Marion led the Mavs, each scoring 26 points. Combined, they scored 23 of the Mavs' 28 points in the fourth quarter.
Russell Westbrook had a game-high 31 points, while Durant and James Harden added 23 points.
Despite the Thunder's big three coming up huge, the Mavs were just too much. Dallas scored 10 points in its last four possessions, while Oklahoma City managed only two points on its last six possessions.
“It's hard,” Harden said. “We let our last two games slip away. There's no excuse. We had two opportunities, two great opportunities with leads at home and on the road.
“We just have to close those games out. There's no excuse. We just have to be better.”
The Thunder will have the offseason to try and cure what ails them. They have about five months before the season opener.
Five long months.
“It's kind of shocking,” Durant said, “that our season is over.”