Khris Middleton starred as the Milwaukee Bucks, their backs against the wall and star Giannis Antetokounmpo injured, beat the Miami Heat 118-115 in overtime on Sunday to stay alive in the NBA playoffs.

With reigning NBA Most Valuable Player Antetokounmpo ruled out after aggravating his sprained right ankle in the first half, Middleton stepped up to score 36 points -- including nine of the Bucks' 11 in overtime.

A Middleton three-pointer put Milwaukee up 116-112 with 6.9 seconds left in the extra session. Miami rookie Tyler Herro drained a three-pointer to close the gap to 116-115 before Middleton made two free throws to seal the win.

Middleton led six Bucks players to score in double figures in the must-win game.

Milwaukee, the Eastern Conference top seeds after posting the league's best regular-season record, trimmed the deficit in the best-of-seven Eastern Conference semi-final to 3-1.

Milawukee star Giannis Antetokounmpo gingerly leaves the court after re-injuring his right ankle in the first half of the Bucks' must-win NBA playoff series game four against the Miami Heat Milawukee star Giannis Antetokounmpo gingerly leaves the court after re-injuring his right ankle in the first half of the Bucks' must-win NBA playoff series game four against the Miami Heat Photo: GETTY IMAGES NORTH AMERICA / Douglas P. DeFelice

They still have a mountain to climb as they try to become the first NBA team to rally from an 0-3 deficit to win a series.

"We all fought," Middleton said. "Especially with Giannis going down the way he did. He came out and tried to fight for us with a bad ankle. We wanted to have his back and just fight for him and fight for everybody."

Antetokounmpo had rolled his right ankle in the Bucks' game-three defeat and twisted it again and went down hard in the second quarter.

He stayed in the game and shot two free throws, making one, before limping to the locker room, clearly emotional as he was assisted by team personnel.

The Bucks, leading 50-48 at halftime, announced that he would not return to the game.

Milwaukee's Khris Middleton drives the to the basket in the Bucks' 118-115 overtime win over the Miami Heat in game four of their NBA playoff series Milwaukee's Khris Middleton drives the to the basket in the Bucks' 118-115 overtime win over the Miami Heat in game four of their NBA playoff series Photo: GETTY IMAGES NORTH AMERICA / Douglas P. DeFelice

"Giannis put it all out there for us," said Milwaukee's Eric Bledsoe, who scored 14 points and pulled down 10 rebounds. "We wanted to come out and get this win by taking it one play, one possession at a time."

Heat forward Jimmy Butler said Antetokounmpo's exit affected Miami, too.

"It shouldn't affect us, but I think that we relaxed a little bit," said Butler, who scored 17 points. Bam Adebayo led the Heat with 26 points, 12 rebounds and eight assists.

Antetokounmpo's departure was a huge blow for the Bucks. He has already been named the league's defensive player of the year and is a heavy favorite to scoop a second straight MVP award after averaging 29.5 points per game, 13.6 rebounds and 56 assists.

But Middleton came through in his absence, scoring 21 points in the third quarter to send the Bucks into the final frame trailing by three.

Middleton was 0-for-6 in the fourth, but Brook Lopez poured in 10 of his 14 for the Bucks. After Herro put the Heat up 107-106 with a three-pointer Milwaukee's Donte DiVicenzo drained one of two free throws to force overtime.

Butler remained confident the Heat have what it takes to close out the series, if they bring the same urgency they did to the first three games.

"We did what I always say you can't do, which is get comfortable," he said. "We thought this one was going to be easy and it was not."