BROOKLYN, N.Y. — Ever since the Brooklyn Nets put together their Big 3 of Kevin Durant, Kyrie Irving and James Harden four months ago, the basketball world has waited to see what these Nets would look like in the playoffs. While it took a bit for the show to get going, things eventually started to look like everyone expected them to.

Following a sluggish first half that saw Brooklyn go 1-for-13 from 3-point range and trail the Boston Celtics by six at halftime, Durant, Irving and Harden combined to score the first 22 points of the second half for the Nets, powering an 18-4 run to open the third quarter by themselves and lift Brooklyn to a 104-93 victory.

“I liked the way we fought,” said Harden, who had 21 points, nine rebounds, eight assists and four steals. “It just shows every game isn’t gonna be perfect.”

Brooklyn’s playoff debut was far from perfect, especially in the first half. The Nets, who finished with the league’s top offense during the regular season, couldn’t hit the broadside of a barn to start the game. Despite getting plenty of open looks, Brooklyn went 0-for-9 from 3-point range in the first quarter, part of a 6-for-23 shooting split in the opening 12 minutes that allowed Boston to take a 21-16 lead.

Things got worse from there for Brooklyn, as the seventh-seeded Celtics went on an 11-4 run to begin the second quarter to eventually take what would turn out to be Boston’s biggest lead, at 32-20, with 9:20 to go in the first half.

But rather than panic at that point, Durant said that the ensuing timeout Nets coach Steve Nash called actually allowed the team to settle down and begin to focus on getting back into the game.

“I know that sounds weird, but we came out of that timeout a little bit more settled and were able to cut the lead to six [at halftime],” Durant said. “We looked at the scoresheet and they made way more 3s than us, and we knew that our offense would start to come around.”

Durant proved to be prophetic and did his best to make sure that would be the case. Playing in his first playoff game since tearing his Achilles in Game 5 of the NBA finals two years ago in Toronto, Durant, who finished with 32 points and 12 rebounds in 39 minutes, opened the second half by making a jumper before drawing a foul and making two free throws on Brooklyn’s first two offensive possessions.

He then blocked a shot to set up a Harden 3-pointer that, less than two minutes into the second half, put Brooklyn back in front. That was followed by Durant, Irving and Harden taking turns burying 3-pointers for Brooklyn, capping that 18-4 in less than five minutes that definitively put the Nets in front for good.

“[Kevin] came out and was extremely aggressive, [and] got to the free throw line [to] start that third quarter,” said Irving, who finished with 29 points on 11-for-20 shooting against his former team. “So I think when one of our leaders on our team sets the precedent, sets the tone, then we follow suit. He got it going. He started attacking the rim and then it started opening up the rest of the floor for us and we made timely shots.”

When asked what caused Brooklyn to get off to such a slow start, several theories cropped up. Nash said the team could still be feeling itself out, even at this stage of the season. This was only the ninth game that Durant, Irving and Harden have played together since Harden was acquired in the blockbuster trade with the Houston Rockets in mid-January. And it was the first time all season that the Nets started the three of them, Joe Harris and Blake Griffin together, in what became the 38th starting lineup Nash has used in what is now 73 games for Brooklyn this season.

“There was a little bit of newness in many ways,” Nash said. “We weren’t sharp offensively, but we found a way.”

Then there was the crowd inside Barclays Center, with 14,391 fans in the building as New York City joined many localities around the country in increasing capacity for the number of fans in attendance. Harden admitted that threw him off a bit, after spending so much of this season playing in front of sparse crowds — or no fans at all — due to the ongoing COVID-19 pandemic.

“In that first half, shots just didn’t go in,” Harden said. “Maybe I’m speaking for myself, but the crowd kind of just threw me off a little bit. It was pretty loud in there. The vibe was what we’ve been missing, and it just threw me off a little bit.

“That second half we got more comfortable and shots started to fall when we needed it to.”

Credit was also given to Celtics big man Robert Williams, who had nine blocked shots and wreaked all sorts of havoc in the paint for Boston. Williams made his presence felt despite playing through a case of turf toe that has held him out of several recent games and forced him to leave Tuesday’s play-in tournament win over the Washington Wizards.

Mostly, though, the Nets collectively shrugged about their offensive issues to start the game. Instead, Brooklyn focused on its defense, which held the Celtics to 40 points in the second half and forced Boston star Jayson Tatum into missing all six of his field goal attempts.

For the game, the Celtics shot just 36.9 percent from the field, and after a hot start from deep Boston finished 11-for-30 from 3-point range, including 2-for-13 in the second half.

For a team that hasn’t exactly been known for its defense all season, the Nets said they need to continue to have that kind of focus moving forward if they want to make the kind of playoff run they hope to.

“We stuck with our defense,” Durant said. “We didn’t let that get in the way of what we wanted to do out there. We helped each other and boxed out well. We’ve got to keep that same effort going into Game 2.”