MIAMI — LeBron James better get well fast. He’s about to play for a championship.

Hardly able to move, James returned from a left leg injury to make the tiebreaking 3-pointer with 2:54 remaining, and the Miami Heat held off Russell Westbrook and the Oklahoma City Thunder for a 104-98 victory on Tuesday night and a 3-1 lead in the NBA finals.

With James watching the final moments, Mario Chalmers finished off a stellar 25-point effort that matched Dwyane Wade. James had 26 points, 12 assists and nine rebounds, only missing a triple-double because he was on the bench at the end after hurting his leg in a fall near the Thunder basket.

Game 5 is Thursday night, and James will have a chance to finish a championship chase that started in Cleveland before he famously — or infamously — left for South Florida before last season. No team has blown a 3-1 lead in the finals.

Westbrook scored 43 points for the Thunder, which wasted an early 17-point lead but was never out of the game because of its sensational point guard. Kevin Durant had 28 points, but James Harden threw in another clunker, finishing with eight points on 2-of-10 shooting. Westbrook and Durant were the only Thunder players to score in the last 16:46.

James stumbled to the court on a drive midway through the fourth quarter, staying on the offensive end of the floor as the Heat regained possession on a blocked shot, and he made a short jumper that made it 92-90.

After Westbrook missed a jumper, the Heat called timeout as James gingerly went to the court. Unable to walk off, he was carried to the sideline by two teammates.

He returned to a huge roar with a little over 4 minutes left and the Heat down two, and after Chris Bosh tied it, James slowly walked into a pull-up 3-point attempt — perhaps doing so knowing he couldn’t drive by anyone.

That made it 97-94, and when Wade followed with a layup with 2:19 left, the Heat finally enough room to withstand Westbrook, who kept coming all night.

“Whatever it takes. No excuses,” said Wade, who had to shake off his own aches and pains after landing hard on his back in the first half following a spectacular block by Serge Ibaka. “You don’t want to leave this arena saying you missed opportunities.”

Chalmers sure didn’t. The player who was struggling so badly that the Thunder put Durant on him in hopes of avoiding further foul trouble made 9 of 15 shots, scoring more points than he had in the previous three games.

“Mario Chalmers is a winner,” Wade added. “He’s due for a big game and he came through for us.”

The Heat couldn’t have done it without James, who refused to let any pain prevent him from taking the biggest step of his career.

The Heat never got past its second finals victory last year, with James’ struggles the biggest problem as Miami lost the last three to Dallas. But he was at his brilliant best in this one, keeping up his scoring surge but also willingly kicking it out to open teammates whenever he was double-teamed.

He tried to play through the pain, but the Heat had to call another timeout and remove him for good shortly after his go-ahead basket. There was no immediate word on the extent of his injury.

Bosh finished with 13 points and nine rebounds for the Heat, which quickly climbed out of the 17-point hole by scoring 16 straight points, with Chalmers and backup Norris Cole helping steady things until James and Wade got going.

James and Durant sat alone on their benches moments before the game, Durant staring quietly toward the floor and James saying something to pump himself up. Then they went out to start, and this time Durant stayed away from him.

In foul trouble the previous two games, he began the game covering Chalmers, an adjustment that freed him from the burden of defending James. It kept Durant safe from fouls — but the Thunder probably didn’t count on the scoring explosion from Chalmers after he had totaled just five over the previous two games.

Neither team could gain separation during a dizzying middle two periods, one score quickly answered on the other end as Miami took a 79-75 lead to the final 12 minutes.

Westbrook hit his first four shots and the Thunder made six of its first seven in a 13-3 burst out of the gate. A run of six straight made it 23-12 against the stunned Heat, which started 5 of 17, and it grew to 33-17 on Harden’s fast-break layup with 21 seconds left.

The Heat found its spark in Cole, who hit a 3-pointer and then opened the second quarter with another to kick off a 16-0 burst, and the Heat would come all the way back to tie it at 35 on Wade’ 3-pointer with 7:57 remaining in the half.

With the crowd back in it, Bosh got them even more fired up by diving on the floor for a loose ball, then leaping up after he was fouled and screaming toward the fans.

Yet the Thunder never gave up the lead, Westbrook constantly coming through with a bucket every time the Heat seemed to get within one point in the final minutes. The Thunder took a 49-46 lead into the break after Shane Battier missed a 3-point attempt just before the buzzer.

Miami went in front in the third, Wade hitting two free throws and a basket that made it 50-49.