BOSTON — The Celtics acquired David Lee and Amir Johnson this offseason with the hopes of providing some extra muscle up front.

But it was a pair of homegrown talents who did the heavy lifting for Boston on Friday night.

Jared Sullinger led all scorers with 21 points and Kelly Olynyk was right behind him with 19 as the Celtics’ offense finally came to life in a 118-98 win at TD Garden.

Sullinger and Olynyk’s production came at a crucial juncture. Boston’s stable of big men had struggled to find their game through the first four contests and accounted for just 21 total points in Wednesday’s road loss to the Indiana Pacers.

But Sullinger was on from the start Friday night, scoring 11 quick points in the first quarter and going 9 for 13 overall from the floor while hitting three of his four 3-point attempts.

“They really (fell) back on the jump shot,” Sullinger said after the game, “because of the way I shot the ball in the preseason — which was horrible. Now that my shot’s coming, I’m just shooting the open shot.”

Olynyk, who hadn’t scored a single point since last Friday, did a little bit of everything. He went 7 for 11 on the night and hit three of five 3-pointers, added seven rebounds and a team-high four steals while finishing with a ridiculous plus-minus of plus-29.

“I just thought he was aggressive right out of the gate,” head coach Brad Stevens said of Olynyk after the game. “… He’s a very talented player — we’ve talked about that — and we need him to shoot it well for us to be a good team. We don’t need him to be the greatest shooter ever, but we need him to be a threat. So it was good for all of us to see that, and he had a great impact on (Friday night’s) game, I thought.”

The good news about having Boston’s depth up front is that any of the team’s five bigs can give a jolt to the offense on a given night. That certainly was the case during a game where David Lee played less than 13 minutes, Tyler Zeller didn’t get in until garbage time and Amir Johnson hit just two field goals.

“Multiple guys played and shot well,” Stevens added. “And a couple of those guys, we need (them) to score for us to be a good team.”

Thumbnail photo via Mark L. Baer/USA TODAY Sports Images

Thumbnail photo via Boston Celtics forward Jared Sullinger (7) celebrates against the Washington Wizards during the second half at TD Garden.