Celtics knocked down hard, but with chance to clinch at home

DALLAS  — Jayson Tatum had his step-back 3-pointer swatted away, then ended up in a heap on the floor and was called for an offensive foul.

It was that kind of night for Tatum and the Boston Celtics, who got knocked down hard in Game 4 of the NBA Finals when they had a chance to complete a sweep of the Dallas Mavericks.

Instead of wrapping up an unprecedented 18th NBA title, the Celtics suffered their worst loss ever in the NBA Finals — and one of the worst in league history — when they fell 122-84 on Friday night.

The Celtics’ 10-game postseason winning streak, a franchise record, ended after they lost on the road for the first time in these playoffs. They had been 7-0, including a Game 3 win in Dallas.

READ: NBA Finals: Luka Doncic, Mavericks crush Celtics to avoid sweep

Now the Celtics will get a chance to clinch it at home. Game 5 is in Boston on Monday night.

Dallas already had a 26-point lead at halftime, and any thoughts of a rally by the Celtics were pretty much done less than two minutes into the second half when Tatum had his shot blocked by Daniel Gafford, with the Boston forward reaching out as he fell and getting whistled for the foul.

With the outcome already all but certain, coach Joe Mazzulla emptied his bench with 3:18 left in the third quarter. It was already a 36-point margin that grew to as much as 48.

Tatum, who had 15 points and five rebounds, was on the bench with Jaylen Brown and the rest of the starters for the remainder of the night. And 7-foot-2 center Kristaps Porzingis never even removed his warmups after being declared available before the game.

There have been only two more lopsided games this late in the season: Boston’s 131-92 win over the Lakers in Game 6 to wrap up the Celtics’ last championship in 2008; and Chicago’s record 42-point win over Utah in Game 3 in 1998.

Boston had its lowest-scoring half all season — regular season and playoffs combined — when trailing 61-35 at halftime.