Stephen A. Smith says Kelly Olynyk looked "virtually unstoppable" as he scored 26 points off the bench in Game 7. (1:47)

BOSTON -- Late in the fourth quarter, after his 3-pointer put the Boston Celtics out front by double digits, the TD Garden faithful celebrated Kelly Olynyk's improbable Game 7 performance by chanting his name.

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"Kelly! Kelly! Kelly!"

Isaiah Thomas talked for the previous 72 hours about how legends were born in Game 7. But on a night when both Thomas and Bradley Beal were spectacular, it was Boston's 7-foot backup center who somehow stole the show.

Olynyk scored 12 of his career-playoff-high 26 points over a three-and-a-half-minute stretch of the fourth quarter as the Celtics emerged with a 115-105 triumph over the Washington Wizards in Game 7 of their Eastern Conference semifinal series.

Boston is headed back to the Eastern Conference finals for the first time since 2012. The top-seeded Celtics host the second-seeded Cleveland Cavaliers in Game 1 on Wednesday night at TD Garden.

Seated together at the podium following Game 7, Thomas dubbed Olynyk the "MVP" of the game. Asked if he heard the repeated "Kelly!" chants from the Garden crowd, Olynyk offered, "I did hear that, in between MVP chants for Isaiah."

Olynyk is the first Celtics reserve to score 25-plus points in a playoff game since Eddie House scored 31 on May 6, 2009, against the Orlando Magic. Olynyk's 26 points were the most by any bench player in a Game 7 since Leandro Barbosa scored 26 points for the Suns in a 2006 playoff game against the Lakers, according to ESPN Stats & Information research.

Olynyk finished 10-of-14 shooting overall, all four of his misses coming from behind the 3-point arc, where he typically does his damage. But on this night, Olynyk picked the Wizards apart inside, feasting when the defense rushed to contest Thomas, who finished with a team-high 29 points. Olynyk was also perfect on all six of his field goal attempts that were contested in Game 7.

Olynyk often implored the Garden crowd to get loud during the fourth quarter, and the fans showered him with a standing ovation when he checked out with 1:37 to play.

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"It was unbelievable. Especially to do it in front of our fans, the city of Boston," Olynyk said. "It was unbelievable to be in there, feel that energy, and feel that enthusiasm -- the passion that 20,000 people have and just thrive off that. It was pretty special to be a part of. Hopefully we can relive that."

Celtics big man Al Horford, playing alongside Olynyk for much of Game 7, said he always knew Olynyk had that sort of effort in him.

"I told him before the series, 'You're going to have a great series,'" Horford said. "Kelly is such a hard worker. Probably the hardest-working guy on the team. His ability is unbelievable. I'm just happy to see him out there having fun and really coming together in the biggest game of the season for us.

"He hasn’t played like this all year. He probably hasn't played like this in his career. But you can see it. Kelly can really score the ball. He's one of those unique bigs that can play inside and out. And I'm just happy that he was able to impact this big game tonight."

Olynyk is scheduled to be a restricted free agent this summer. The Celtics are hoping to have enough available cap space to chase a big-ticket free agent, but it's likely the team will try to make Olynyk a priority, too, particularly if he can step up like he did on the big stage.

The conversation about Olynyk early in the series centered on whether he was a dirty player after a Game 3 dust-up with Kelly Oubre Jr. On Monday night, as the Celtics leaned hard on Olynyk in the biggest game of the season, Oubre was essentially a DNP for the Wizards, playing just 6 seconds.

Beal finished with a game-high 38 points and allowed the Wizards to hang around in the fourth quarter. John Wall finished with just 18 points on 8-of-23 shooting overall and, over the final 19 minutes of play, went scoreless while missing his last 11 shots (including seven 3-pointers).

TD Garden felt tense for the entirety of the middle quarters, and the Wall/Beal tandem seemed to have an answer each time Boston went on a brief run to pull close. Over the final 1:46 of the third quarter, Thomas and Marcus Smart combined for a trio of 3-pointers as the Celtics closed on a 9-0 burst to take a six-point lead into the final frame.

Boston ultimately stretched its run to 18-2, culminating with Thomas' straightaway 3-pointer that had the Celtics out front 94-81 with 10 minutes to play. The Wizards called timeout and immediately responded with a 7-0 run that forced Celtics coach Brad Stevens to call his own timeout to settle his players with Boston's lead down to six.

That's when Olynyk went to work and ensured Boston's spot in the conference finals.

There was a five-minute stretch in the fourth quarter where Kelly Olynyk outscored the Wizards 12-10. ESPN Stats & Info

"[Olynyk] stepped up and had a great game," Wizards coach Scott Brooks said. "He made a lot of shots tonight, you've got to give him credit, he stepped up big for them tonight."

Olynyk, whose stats this season were noticeably better when he played in a man bun as opposed to a headband, was asked if he'd be sticking with the man bun that he thrived with in Game 7.

"It's a good question," Olynyk said. "Time will tell."

From his Area 21 Twitter account, Kevin Garnett even shouted out Olynyk while offering his famed 2008 proclamation, "Anything is possible!" then adding the hashtag, "#Manbuns."

The Wizards were bidding for their first trip beyond the second round since 1979. That year, the top-seeded Bullets beat San Antonio in the East finals before falling to Seattle in five games in the NBA Finals. Instead, the Celtics won their record 22nd Game 7 in franchise history. They now own a 22-8 (.733) all-time record in Game 7s and the best Game 7 win percentage in NBA history, minimum two Game 7s.