DALLAS (AP) — Luka Doncic scored 25 of his 29 points in the first half, Kyrie Irving added 21 points and the Dallas Mavericks emphatically extended their season on Friday night, fending off elimination by beating the Boston Celtics 122-84 in Game 4 of the NBA Finals.

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.

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.

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.

The loss — Boston’s first in five weeks — snapped the Celtics’ franchise-record, 10-game postseason winning streak, 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.

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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.

And they were off and running from there. And kept running.

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.

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

— The 35 points represented the Celtics’ lowest-scoring total in a half, either half, in Joe 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.

The Mavs still have the steepest climb possible in this series, but the first step was done.

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