The Mavericks never looked back, building a double-digit lead in the first quarter and taking a 61-35 halftime lead against the Celtics, who will get their second chance at their first title since 2008 during Game 5 on Monday at TD Garden. Boston’s embarrassing no-show performance marked the third-worst playoff loss in franchise history, topped only by a 47-point loss to the Orlando Magic in 1995 and a 44-point loss to the Cleveland Cavaliers in 2017. Dallas’ 38-point win was the second-largest playoff margin In franchise history.

“We don’t have to complicate things,” Mavericks coach Jason Kidd said. “This is not a surgery. Our group was ready to go. We took a stand. We were desperate. The hardest thing in this league is closing the door on a group that has nothing to lose. Tonight I saw that. [The Celtics] Let go of the rope too early.

Lively’s 3-pointers weren’t entirely unprecedented — he made two during his rookie season at Duke — but they pleased an anxious home crowd and lightened the mood for the Mavericks, who had struggled to score in the first three games of the series and absorbed significant criticism in the wake of Luka Doncic’s foul. Late in a tight third game.

With the pressure temporarily eased, Doncic finished with a game-high 29 points, in addition to five rebounds and five assists in just 33 minutes, and Dallas achieved a high scoring balance for the first time against Boston’s strong defense. Five Mavericks scored in double figures, and the Mavericks went 15 points on 37 (40.5 percent) on 3-pointers — their best shooting performance from the field in the Finals.

“[Doncic] “He was doing everything for us,” Kidd said. “He played his game tonight. We talked about playing faster, and I thought he set the pace for us. There was no different Luca there. He was fantastic. He was great. He is one of the best players in the world. As much as we want to criticize him, he is Great player.”

Celtics center Kristaps Porzingis missed his second straight game with a left ankle injury, and the Mavericks regularly took advantage of his absence by creating quality opportunities in the paint. Irving added 21 points, four rebounds and six assists to end a personal 13-game losing streak against his former team, the Celtics.

After Celtics coach Joe Mazzola spent the past three days preaching against mental stagnation, his team’s offense started flat and then fell further as the game unfolded. Jayson Tatum scored 15 points — all in the first half — but it wasn’t enough for Boston to earn its first Finals sweep since the 2017-18 season with the Golden State Warriors. Jaylen Brown, an early Finals MVP candidate, had a dismal performance with 10 points on 3-for-12 shooting, looking out of sync from the opening tip.

“I think this is the slumpest of the series,” Tatum said. “[This was] The worst job is having our space on the offensive side, and [not] Doing what we wanted to do instead of what they were forcing us to do. We did a great job in the first three games. We didn’t do this.”

As thousands of Celtics fans packed into Texas hoping to celebrate the title, their pregame expectations gave way to a slump in their shoulders at the start of the second half. Boston suffered its first playoff defeat in eight games on the road, and the loss snapped a 10-game winning streak dating back to a second-round series against the Cleveland Cavaliers.

“Dallas is a great team,” said Mazzola, who avoided criticizing the Celtics. “We’re going to have to earn it. [Our effort] It wasn’t as good as Dallas. “They were doing much better.”

After being held to fewer than 100 points in its first three Finals games, Dallas got there with just over nine minutes left, leading by as many as 48 points. Mazzola withdraws his starters 15 minutes before the end of the match. The fourth quarter was a bad time, though, as Mavericks guard Tim Hardaway Jr. let out screams of joy and “Mavs in seven!” Cheers for breaking out of a month-long slump to finish with 15 points on five 3-pointers.

For Doncic, who was angry after losing Game 3, the big win led to a big smile after the game and continued belief that Dallas can break NBA history. Teams, like the Celtics, that have won the first three games of a seven-game series, are 156-0 in NBA playoff history and 14-0 in the Finals.

“We will believe until the end,” Doncic said. “We just have to keep going. I have a lot of confidence in this team that we can get it done. … Everyone played with a lot of energy. That’s the way we have to do it. We have to think the same way in Game 5 in Boston.”

The Celtics will have a couple of days off to ponder why they lack the energy to close out the series in emphatic fashion. As the Mavericks proved in the Western Conference Finals against the Minnesota Timberwolves, a Game 5 masterpiece has the potential to erase all memories of a failed Game 4.

“They played a lot better than us,” Celtics quarterback Al Horford said. “They clearly outplayed us. It’s hard to accept, but that’s the reality. The one thing I can tell you about our group is that we’ve responded time and time again when faced with adversity.