DALLAS (AP) — There were two options for the Dallas Mavericks. Pack for Boston, or pack for vacation.

Boston awaits.

These NBA Finals are not over, thanks to one of the biggest blowouts in title-round history. Luka Doncic scored 25 of his 29 points in the first half, Kyrie Irving added 21 and the Mavericks emphatically extended their season on Friday night, fending off elimination with a 122-84 rout of the Celtics in Game 4.

The 38-point final margin was the third-biggest ever in an NBA Finals game, behind only Chicago beating Utah 96-54 in 1998 and the Celtics beating the Los Angeles Lakers 131-92 in 2008.

“It's real simple. We don't have to complicate this. This isn't surgery,” Mavericks coach Jason Kidd said. “Our group was ready to go. They were ready to celebrate and we made a stand. We were desperate. We've got to continue to keep playing that way. They're trying to close the door. The hardest thing in this league is to close the door when you have a group that has nothing to lose. Tonight, you saw that.”

The Mavs' stars were done by the end of the third quarter, with good reason. It was all Dallas from the outset, the Mavs leading by 13 after one quarter, 26 at the half and by as many as 38 in the third before both sides emptied the benches.

Before Friday, the worst NBA Finals loss for the 17-time champion Celtics was 137-104 to the Lakers in 1984. This was worse. Much worse, at times. Dallas' biggest lead in the fourth was 48 — the biggest deficit the Celtics have faced all season.

The Celtics still lead the series 3-1, and Game 5 is in Boston on Monday.

“Preparation doesn’t guarantee an automatic success,” Celtics coach Joe Mazzulla said. “I thought we had a great process. I thought we had a great shootaround. Thought we had a great film session yesterday. I thought the guys came out with the right intentions. I just didn’t think it went our way, and I thought Dallas outplayed us. They just played harder.”

The loss — Boston’s first in five weeks — snapped the Celtics’ 10-game postseason winning streak, longest in franchise history, plus took away the chance they had at being the first team in NBA history to win both the conference finals and the finals in 4-0 sweeps.

Jayson Tatum scored 15 points, Sam Hauser had 14 while Jaylen Brown and Jrue Holiday each finished with 10 for the Celtics.

Tim Hardaway Jr. scored 15 points, all in the fourth quarter, and Dereck Lively II had 11 points and 12 rebounds for Dallas. It was Lively who provided the hint that it was going to be a good night for the Mavs in the early going. He connected on a 3-pointer — the first of his NBA career — midway through the first quarter, a shot that gave the Mavs the lead for good.

They were off and running. And kept running.

“It doesn't change anything,” Doncic said. “Like I said in the beginning of this series, it's the first to four. And we're going to believe until the end. We're just going to keep going. I have big belief in this team that we can do it.”

It was 61-35 at the half and Dallas left a ton of points unclaimed in the opening 24 minutes as well. The Mavs went into the break having shot only 5 of 15 from 3-point range, 10 of 16 from the foul line — and they were in total control anyway.

“I think winning is hard. I think winning at any game is hard. But winning Game 4 of the NBA Finals is pretty damn hard,” Holiday said. “I think they came out desperate and I think they punched us in the mouth, and we couldn’t kind of recover the way we wanted to.”

The first-half lowlights for Boston were many, some of them historic:

— The 35 points represented the Celtics’ lowest-scoring total in a half, either half, in Mazzulla’s two seasons as coach.

— The 26-point halftime deficit was Boston’s second biggest of the season. The Celtics trailed Milwaukee by 37 at the break on Jan. 11, one of only eight instances in their first 99 games of this season where they trailed by double figures at halftime.

— The halftime deficit was Boston’s largest ever in an NBA Finals game, and the 35-point number was the second-worst by the Celtics in the first half of one. They managed 31 against the Lakers on June 15, 2010, Game 6 of the series that the Lakers claimed with a Game 7 victory.

Teams with a lead of 23 or more points at halftime, even in this season where comebacks looked easier than ever before, were 76-0 this season entering Friday night.

Make it 77-0 now. Doncic’s jersey number, coincidentally enough.

The Celtics surely were thinking about how making a little dent in the Dallas lead to open the second half could have made things interesting. Instead, the Mavs put things away and fast; a 15-7 run over the first 4:32 of the third pushed Dallas’ lead out to 76-42.

Whatever hope Boston had of a pulling off a huge rally and capping off a sweep was long gone. Mazzulla pulled the starters, all of them, simultaneously with 3:18 left in the third and Dallas leading 88-52.

“I expect us to be much better on Monday,” Celtics center Al Horford said.

The Mavs still have the steepest climb possible in this series — no team has successfully rallied from 3-0 down in NBA history — but the first step is done.

“We have nothing to lose,” Kidd said.

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