Oklahoma City forward Kevin Durant has vowed to make amends for his flawed performance in the last game of the NBA finals when the Thunder square off against Miami Heat in Wednesday's fourth game.

The three-time NBA scoring champion was restricted to 25 points, including just four in the final quarter when the pressure was really on.

He was benched in the third quarter when he earned his fourth foul, shot just two from six in the fourth, and missed two free throws as the Thunder blew a 10-point lead to lose 91-85 and trail 2-1 in the best of seven series.

"I missed a three that went in and out, I missed a few shots going to the rim," the 23-year-old said. "But I'm going to shoot until my arm falls off in the fourth."

But Durant, who often juggles his scoring responsibilities with the dubious task of defending LeBron James, said he had lost none of his self belief and pledged to play better over the rest of the series.

"That's what I do. I believe in myself," he said.

"I've got 100 percent confidence in myself that I can do it, and when the fourth quarter comes around next time, I'm going to be as aggressive as I can."

Although Miami still need to win two more games to win the championship, the odds are starting to mount up in their favor.

The team that wins game three has gone on to win the title 85 per cent of the time, and Oklahoma guard James Harden said it was inconceivable the Thunder could let Miami win game four.

"Tomorrow's game is like a game seven," Harden told reporters before hitting the practice court on Monday. "Our backs are against the wall.

"We can't go down 3-1 and give them an opportunity to close it out in five. We need to make it 2-2 and a best-of-three with two games in Oklahoma City."

The first three games have all fluctuated widely and Oklahoma center Kendrick Perkins said he expected more momentum swings in game four.

"The team that gets the win always gets the momentum," said Perkins, who won an NBA title with the Boston Celtics.

"At the end of the day, we're just down one game, and it's not the end of the world."

Oklahoma guard Russell Westbrook, who was also benched because of foul trouble, also remained upbeat, saying the Thunder believed they should be leading the series and were confident of turning things around.

"We felt we let two games get away," he said. "And tomorrow we have an opportunity to win again."

(Editing by Julian Linden)