Boston Celtics guard Kyrie Irving (11) shoots between Washington Wizards forward Kelly Oubre Jr. (12), guard John Wall (2), and guard Austin Rivers, right, during the second half of an NBA basketball game Wednesday in Washington. The Celtics won 130-125 in overtime. Credit: Alex Brandon | AP

Kyrie Irving was the last player inside the visiting locker room of Capital One Arena on Wednesday night. A group of his Boston Celtics teammates had already left for the bus as he sat alone at his stall. He looked drained, a bag of ice strapped to both his shoulders and both his knees, his feet icing in a big blue bucket.

Irving was in no rush. He has always loved playing in this arena and has his own ritual of honking the horn of the small security vehicles parked in the tunnels beyond the court. He pressed it again a few times Wednesday night after he had scored 38 points in 40 grueling minutes to lead the Celtics to a 130-125 overtime win over the Washington Wizards.

“I honk the horn every time. It’s just a thing I have with security here, it’s nothing personal against anybody,” Irving said. “I’m feeling good and making sure we’re playing the right way.”

Boston (17-10) has won seven straight after starting the season with a mediocre 10-10 record, and Wednesday night provided the latest proof that this team has re-established itself as a contender in the Eastern Conference. It would not have been possible without adaptability for a roster that has dealt with rotating injuries through the first two months of the season, nor without the play of Marcus Morris or Marcus Smart, both who were moved into the starting lineup late last month and combined for 45 points Wednesday night. But Irving, who has implored his team to have more fun, has also elevated his game over this stretch.

He scored 12 points in overtime Wednesday night, and the final 38 seconds belonged to him. It included a 27-foot 3-pointer in front of his own bench with a hand-in his face, a 31-foot 3-pointer from beyond the top of the key that finally got his team a lead it wouldn’t relinquish, and a pair of victory-sealing free throws in the final seconds that were serenaded with M-V-P chants from the road crowd.

“Those last two shots were amazing. The one in front of our bench was a joke,” said Celtics coach Brad Stevens, who watched as Irving had fun with it afterward too, handing his sneakers to a kid sporting his jersey, running into the tunnel and honking a security vehicle’s horn, laughing on his cell phone in the locker room as he iced his exhausted body. It felt different than a short month ago, when Boston was struggling to find continuity and consistency with its lineups.

“The hallmark of this team,” Stevens said, “is that whoever is available, plays.”

It entered Wednesday night’s game having won six in a row by an average of 26 points, but there were question marks before this road test began. Irving had already missed a game earlier this week with a sore shoulder. Center Al Horford and forward Gordon Hayward sat out Wednesday with injuries, and Jaylen Brown was a late scratch due to an illness. Those absences were compounded by an ugly first half. The Celtics shot just 4-for-20 from 3-point range — it had just six assisted field goals in the first two quarters — and attempted just four free throws. Washington led by 11 at one point and Boston looked as if it might revert to its mid-November self.

“We came back to the locker room and looked at the stats,” Morris said. “We seen what we were doing. We knew we just had to move the ball.”

Morris’s energy and versatility, which made him a natural fit for Stevens to insert into the starting lineup in late November, was critical as the Celtics made a push in the third quarter. Even as Stevens was forced to go small, the Celtics looked comfortable. Morris finished with 27 points and nine rebounds, while the 6-foot-4, 220-pound Smart played center in the fourth quarter. It was the first time since high school he had played the position, but it was significant on a night when his primary assignment was to hound Wizards guard Bradley Beal. He moved to the spot — he’s now played all five positions for Stevens — and came up with two crucial offensive rebounds beginning in overtime, both of which led to buckets.

“It was more of a stretch-six tonight. But it’s just what we needed tonight,” Smart said.

It’s that mentality that has Boston believing it can recapture its dominant standing in the Eastern Conference, even with the litany of injuries.

“Our spirit is good,” Stevens said.

The players are having fun again at least, Irving said. He was the last to leave the locker room, throwing a hood over his head and hustling to the bus. He was running late but stopped to sign autographs and chat with Beal, with whom he shared one last laugh.

“When you have inner peace, it makes your job a lot easier,” he said after his team’s latest win. “You have to enjoy the pain and suffering as much as you enjoy the happiness.”