Durant scored 24 points, Harden kept his late-season surge going with 22 points and the Thunder beat the Detroit Pistons 104-94 on Friday night.
Harden, the No. 3 pick in the 2009 draft, was scoring 10.3 points per game before the All-Star break but is averaging 17.7 in 10 games since.
"Losing Jeff, you lose 15 points, you lose more rebounds, just more playmaking ability," Harden said. "I had to step my game up and just help the team."
The continued emergence of Harden has helped the Thunder keep powering on even though they're playing without the two players they got from Boston in the Green trade -- Kendrick Perkins and Nate Robinson -- because of knee injuries
Green was averaging 15.2 points and fellow starter Nenad Krstic, also dealt to the Celtics, averaged 7.6 while with the Thunder.
"When we made the trade, we just needed guys to continue to work on their games, continue to play good basketball and the scoring would find its way onto the floor," coach Scott Brooks said.
"As it's turning out, James has picked it up. But we're not looking to him every game thinking that he has to do that."
Detroit was within four before Westbrook beat the shot clock buzzer with a 3-pointer from the left wing, and Nick Collison bailed out the Thunder again just a handful of possessions later by scooping up a loose ball and banking it in just before the 24 seconds ran out to make it 72-65.
That started a span when Oklahoma City hit its final six shots of the period -- including back-to-back 3-pointers by Harden and another from Thabo Sefolosha that bounced high off the rim before falling through.
The Thunder then scored the first seven points of the fourth quarter and took a 93-75 lead on Harden's fourth 3-pointer of the game.
"Harden is one of those assassins that just doesn't need much of a chance to knock it down," Pistons coach John Kuester said. "He made some big shots. Long shots, too."
Westbrook added 13 points and 11 assists, becoming the fifth player in NBA history to reach 4,000 points, 1,500 assists and 1,000 rebounds during his first three years in the league. The others are Chris Paul, LeBron James, Anfernee Hardaway and Oscar Robertson.
And now, the Thunder seem to have another budding young star.
Harden reeled off a career-best 12 straight games with double-digit scoring that finished on Jan. 4, but then was held to single digits in 11 of his next 12 games and wasn't even picked for the Rookie-Sophomore game at All-Star weekend until Sacramento's Tyreke Evans pulled out at the last minute with a foot injury.
"When we made the trade, I didn't go to James and say, `James, we need six more points from you and you need to do it or else you're not going to play.' I didn't quite say it that way," Brooks said. "But we all understand he's a good player. ... We're finding opportunities for him to score other than a middle pick-and-roll. He's a terrific 3-point shooter. He's a backdoor player. He can come off screens."
Durant said Harden is exactly what the Thunder need coming off the bench, and it's simply a matter of Harden being smart and realizing an opportunity to take on a bigger role.
"He learned all last year what it takes to be a good sixth man. He knows from going to practice first team versus second team that he's the go-to guy on the second team in practice, so that's helping him out," Durant said.
"We look for him. When he comes off that bench, we look for him. He's one of our main options on the offensive end. He's a great scorer."
Detroit stayed close enough to make Durant and Westbrook come back into the game with 5 1/2 minutes left, then scored nine straight points to get within 100-94 on Stuckey's three-point play with 47.1 seconds to play.
Hamilton and Tayshaun Prince even missed 3-pointer during the comeback that could've made it closer.
Instead, the Pistons were forced to foul in the final minute. Westbrook hit two free throws, then missed two before Serge Ibaka tipped in his errant shot to make it 104-94.
Prince finished with 15 points for the Pistons, who allowed an opponent to shoot 50 percent or better for the 30th time this season.
"Defense has been lacking all year," Stuckey said. "We have to get better at it, especially going to play Denver [on Saturday]. They are an up-and-down team, so we are going to have to stay with them. they are going to be running."
Detroit, the league's worst rebounding team, doubled up the Thunder on the boards early and shot 61 percent while jumping out to a 28-22 lead following Hamilton's jumper to open the second quarter.
The Pistons led by seven before Oklahoma City came back. Durant was fouled and hit two free throws on three straight possessions, and Westbrook had right-handed windmill jam during a 16-7 run to finish the first half and put the Thunder up 55-50.
The Thunder are 7-1 this season in overtime games, and their two previous wins both came in OT. "I'm a heck of a five-minute coach. I can coach five minutes," Brooks said. "I don't know what it is. We've played well in overtime, we've got lucky in overtime and we've won a lot of games in overtime. But it's not something you go into thinking, 'I hope we get an overtime game because our win percentage is pretty high." ... The Pistons fell to 19-18 when either leading or tied after the first quarter. They're 4-25 when behind after 12 minutes.