Kevin Durant says James Harden's fresh hamstring injury "sucks" as the Brooklyn Nets brace to lose their star guard for an extended period of time during the NBA playoffs.

Harden was forced out of Saturday's 115-107 Game 1 win over the Milwaukee Bucks after 43 seconds after re-injuring the same hamstring which kept him out of 21 games late in the regular season.

The 31-year-old former MVP was sent for scans on his right hamstring with the extent of the injury unclear at this stage, but Durant spoke like someone not expecting good news.

"It sucks. It sucks. I want him to be out there," Durant told the post-game news conference. "I know how much he cares. I know how much we wants to be in this moment. It sucks.

"I wish him a speedy recovery. We're going to keep him involved as much as possible. It's just a bad break."

The Nets rallied hard to bounce back from the early loss of Harden to overcome the Bucks, who had Giannis Antetokounmpo score 34 points.

Brooklyn's defense was a feature, applying pressure to force the Bucks to shoot at 20 per cent from beyond the arc, while Blake Griffin had 14 rebounds in a throwback game.

Offensively Durant and Irving starred with 29 and 25 points respectively, but the former admitted they had to overcome the emotional blow of Harden's injury.

"We try not to be too emotional out there but losing one of your leaders like that, the first play of the game, we had to re-group for a couple of minutes and figure out what was next," he said.

"The coaching staff did a great job of moving forward. Guys came in and tried to play extremely hard.

"We're going to be thinking about James. I'll definitely call him when I leave him. I hate that it had to happen right now."

Durant refused to look too far ahead about the prospect of a tough Conference semi-final series against the Bucks without Harden.

"I'm not even thinking like that," he said. "I'm taking it a day at a time, a second at a time. Get ready for practise tomorrow.

"We're not really thinking that far. We'll try take it a game at a time and see what happens."

Game 2 between the Nets and Bucks is on Monday.