BOSTON — Moments before Game 7 at TD Garden, the Boston Celtics — a franchise that’s seen a few of these nights — played a pregame pump-up package on the Jumbotron. The video featured legends of the past, from Bill Russell to Larry Bird to Paul Pierce, capped with a single phrase flashing on the screen hanging over a hometown crowd drooling to eat it up: “Now it’s time to write a new chapter.”

They just didn’t realize Kelly Olynyk would be the one to write it.

The Celtics used an 18-2 run spanning the end of the third quarter and the start of the fourth to take command of a game nobody could get a handle on, and Olynyk scored 14 of his 26 points in the fourth to put the finishing touches on a 115-105 win that sent the C’s to the Eastern Conference finals for the first time since 2012. Game 1 against the Cleveland Cavaliers tips Wednesday in Boston at 8:30 p.m. ET.

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This was the same Kelly Olynyk who Celtics president of basketball operations Danny Ainge described as “a 7-foot hippy” upon drafting him at the end of the 2013 lottery — an introduction overshadowed by Boston’s trade of Paul Pierce and Kevin Garnett hours later. The same Kelly Olynyk who was labeled a lumbering brute when he ripped Cavs forward Kevin Love’s shoulder from its socket the last time the two met in the playoffs. The same Kelly Olynyk who scored one point in Game 3 and four in Game 6.

The same Kelly Olynyk who was asked about his man bun in the postgame press conference.

Isaiah Thomas added 29 points and 12 assists, including back-to-back 3-pointers that gave the Celtics the lead for good late in the third quarter. Al Horford (15 points, six rebounds, five assists), Marcus Smart (13 points, six rebounds, four assists) and rookie Jaylen Brown (nine points, all in momentum-swinging moments) were invaluable, but Olynyk was the difference. His 26 points matched his season high from Jan. 13, and set a new playoff career-high. His previous high-water mark? Fourteen, set in Game 4 of this series — the same number of points he had in the fourth quarter of Game 7 alone.

Olynyk scrawled his Game 7 heroics into Celtics lore, and Boston’s crowd provided the punctuation, chanting “Kelly” on an evening coach Brad Stevens called the loudest of his four years in the arena. “I heard it,” said Olynyk, “in between the MVP chants for Isaiah.” But even Thomas passed that mantle on Monday. “You dream of winning Game 7s, you dream of playing in the Garden, the fans were amazing,” the All-Star said. “We didn’t give up. We gave it our all, and Kelly was the MVP tonight. He did it all.”

Bradley Beal scored a game-high 38 points for the Wizards. Otto Porter (20 points, 10 rebounds) and John Wall (18 points, 11 assists) added double-doubles, while Markieff Morris (18 points, nine rebounds) fell a rebound shy of one. But Wall missed his last 11 shots, including seven 3’s, to finish scoreless in the game’s final 19 minutes, while Washington got just five points off the bench — all from Bojan Bogdanovic — and nothing in the second half beyond more personal fouls from Ian Mahinmi.

“I’m more disappointed we lost more than anything,” said Beal, who finished 12-of-22 from the floor. “I don’t care how well I played. I don’t care if I played bad. The end result and the only thing that matters is getting a win, so these stats really don’t mean too much of nothing to me right now.”

Both teams succumbed to Game 7 jitters early, missing open shots, but the Wizards’ game plan to swarm Thomas led to so many good looks that eventually they started falling for Boston and Olynyk.

“They were putting a lot of attention on [Thomas] — a lot of attention — and he was putting us in great spots,” said Olynyk. “Then, we’re playing 4-on-3, and if they don’t want to run at you or try to run at you too hard, you’ve got to be able to make a basketball play. They weren’t going to let [Isaiah] make plays at the end. They were going to make other people do it, so someone had to do it.”

That someone turned out to be Olynyk, who did everything short of stealing Thomas’ signature fourth-quarter celebration, pointing to his wrist and announcing to everyone watching this was his time.

Still, the game never felt too far out of either team’s hand, not with everyone wound so tight in a winner-take-all contest awash in the roars of a deafening crowd. Either too young to know better or too inexperienced to understand the gravity of it all, rookie Brown and fourth-year man Olynyk provided the depth scoring Boston so sorely lacked in Game 6, each matching the bench’s output on Friday with five points apiece in the first quarter to give Boston a 27-23 lead through 12 minutes.

Exhibit A of those jitters and the Celtics’ ability to manufacture enough to cling to a slim lead:

The Wizards hung tough, as Porter and Morris (23 points and 13 rebounds combined in the first half) picked up the slack left by a slow start from Washington’s star backcourt. Wall was his usual relentless self, though, and Beal never stays cold. The two caught fire late in the second quarter, scoring 11 of the Wizards’ final 14 points before the break and turning that slim deficit into a 55-53 edge at the half.

The nerves were permeating. Even the officials were tense, calling 24 fouls for 34 free throws through two quarters. A trio of Celtics — Olynyk, Smart and Amir Johnson — had three personal fouls apiece at the midway point, and the Boston crowd reminded the referees with a handful of “bulls***” chants.

The Wizards kept riding what was working to take their own six-point lead midway through the third quarter. Beal took the smaller Thomas to the post, and then shot over him from the outside; Wall ran wild; and Porter chipped in. Suddenly, Washington found the open shots Boston enjoyed in the first quarter, taking advantage of some Celtics miscommunication, and the once-raucous fans grew quiet.

The Celtics briefly resuscitated the crowd, tying the game on a Brown steal and alley-oop layup:

But Beal was a monster, pouring in another dozen points in the third quarter and keeping the C’s at bay. With the building growing tauter by the minute, Thomas finally popped the mounting pressure, draining a pair of 3-pointers 45 seconds apart at the end of the frame to give the Celtics their first lead of the second half, and Marcus Smart’s 3 on the ensuing possession took the roof off completely.

After a 9-0 finish to the third, Brown started the fourth quarter with a dunk, and another Thomas 3 a couple minutes later capped an 18-2 run that pushed Boston’s lead to 94-81. It was the first double-digit lead of the game for either team, and a seemingly comfortable cushion with 10 minutes to go.

“This is Game 7 of the Eastern Conference finals,” said Brown. “Two years ago I was just in high school.”

Fittingly in a series full of skirmishes, the Wizards didn’t go down without a fight. A four-point play by Beal slashed Boston’s lead to four with just over six minutes left. Just as fittingly, Olynyk — who famously featured in one of those skirmishes — delivered the knockout blow. The Canadian scored 12 of Boston’s 14 points during a stretch that nudged the lead back to 10 with 3:26 to go, sending Washington home for the summer and the Celtics on to a date with LeBron James and the rested Cavs.

Asked if reaching the conference finals was a stepping stone for a young Celtics team trying to write its own chapter in the franchise’s everlasting pursuit of the next title, Stevens wondered, “If Kelly doesn’t go nuts, and they throw in a couple more 3’s, we’re not talking about the next step, right?”

Yup, Kelly Olynyk sent the Celtics to the Eastern Conference finals, if you can believe it.

“It was ridiculous,” added Stevens. “It was fantastic. It was unbelievable. I tried to tell my friends back in Indiana … that there’s no place like this building in the playoffs. And I’m not sure I’ve ever felt this building reach the level it did tonight, at least since I’ve been here. I wasn’t fortunate enough to live some of those good memories of the past, but hopefully we can keep having nights like tonight.”

Because there’s still another chapter left to write.

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Ben Rohrbach is a contributor for Ball Don’t Lie and Shutdown Corner on Yahoo Sports. Have a tip? Email him at rohrbach_ben@yahoo.com or follow him on Twitter! Follow @brohrbach

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