Kevin Durant shoots over Washington’s Rasual Butler during the second quarter of Friday’s game in Oklahoma City. (Sue Ogrocki/Associated Press)

The Washington Wizards and Oklahoma City Thunder, opponents at Chesapeake Energy Arena on Friday night, opened 2015 seeking to validate expectations. The Wizards, in the midst of their toughest stretch of the season against five of the Western Conference’s best teams on the road, entered with an opportunity to prove they are legitimate contenders after their best start in 36 years.

The Thunder, beset by injuries to their two best players from the season’s outset, is poised to demonstrate it once again belongs among the NBA’s elite with Kevin Durant and Russell Westbrook healthy.

The Thunder’s 109-102 win offered ample evidence of validation on both accounts. For 47 minutes, the Wizards hung tight. But the Thunder one-upped the Wizards with its big-game pedigree, making the crucial plays and capitalizing on Washington’s errors down the stretch.

“We should’ve won the game, man,” Wizards shooting guard Bradley Beal said. “Honestly, I’m not even going to sugarcoat it. I just feel like we gave one away.”

The decisive sequence occurred with less than a minute remaining. The Wizards had the ball trailing, 105-102. But Westbrook intercepted John Wall’s cross-court pass to Beal to spark a back-breaking fast break that concluded with a layup from Serge Ibaka.

The Post Sports Live crew debate whether the Wizards can prove they are Eastern Conference title material with wins on a tough five-game road trip against top Western Conference teams. (Post Sports Live/The Washington Post)

“I lost the game,” Wall said.

The mishap was Wall’s first turnover on a night in which he finished with 14 points and 12 assists. Beal had a team-high 21 points to go with 10 rebounds and six assists for his first double-double of the season. Six Wizards scored in double figures, including Andre Miller, who scored a season-high 15 points in 20 minutes off the bench.

But the Wizards (22-10) didn’t have an answer for Durant. Two nights after pouring in 44 points in his first game back from a six-game absence due to an ankle sprain, Durant scored 34, including nine in the decisive fourth quarter, on 12-for-18 shooting. The former All-Met from Montrose Christian grabbed eight rebounds and went 4 for 7 from behind the three-point line, making a slew of unguardable, well-contested shots to deflate the visitors.

“That’s who he is,” Wizards Coach Randy Wittman said of Durant. “Big players make big plays. He made a couple of them at the end.”

While Durant fueled the Thunder (17-17), Westbrook battled foul trouble most of the night and finished with 22 points on 8-for-23 shooting. Ibaka (13 points) was the only other Thunder starter to score in double figures. The Oklahoma City bench, however, produced 40 points — 11 more than its average — as the Thunder improved to 9-2 with Westbrook and Durant in the lineup, and moved to .500 for the first time this season.

Questionable calls and emotions flooded the first quarter, resulting in three technical fouls in the game’s initial nine minutes. First, Nene was assessed a technical after a shoving match with Thunder center Steven Adams, who was given a personal foul while Durant drained a three-pointer.

Wall then was called for his second foul defending Westbrook in the post. Frustrated, he approached official Bill Kennedy and asked for an explanation. Wall was subsequently assessed a technical foul as he walked to the Wizards’ bench, where he spent the next 11 minutes. The sequence, bizarrely, proved beneficial for the Wizards.

Westbrook, who was ejected from the Thunder’s win over the Phoenix Suns on Wednesday with two technicals, drew the final technical of the period after he followed an elbow to Beal’s face with an outburst.

Up until then, Westbrook and Durant, the reigning MVP, were the only Thunder players to score, netting the team’s first 19 points. In the meantime, the 38-year-old Miller was getting hot. The point guard, the oldest active player in the NBA, scored the Wizards’ final four points of the period and followed it up with a masterful display of fundamentals to start the second quarter.

Cognizant of Westbrook’s foul situation, the deliberate Miller attacked the uber-athletic point guard, generated 13 first-half points, and took center stage on a night when the Westbrook-Wall encounter was the anticipated matchup.

Washington led by two at the half carried the momentum over to the third period, taking an eight-point lead with 1 minute 26 seconds left in the quarter after five straight points for Wall. Oklahoma City closed the period with an 8-0 run to draw even, a stretch Durant completed with consecutive pull-up three-pointers.

“We just wanted to keep it close,” Miller said. “But I think at the end of the third quarter they hit some shots that kind of put them in the game and gave them momentum for the rest of the game.”

From there, the teams were neck-and-neck until the final minute, when the Wizards, who have now lost two of three games on their grueling road trip, ran out of gas.

“That’s what we’re still learning,” Beal said. “It’s been a process for us and the biggest thing is how to keep that lead and how to increase it. . . . We’ll get there. It’s a learning process.”