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On Friday, Dereck Lively II was wide open in the right corner when he caught a kickout pass from Luka Doncic halfway through the first quarter. The Dallas Mavericks' center was ready to shoot, and, without hesitation, he raised up and released it. 

It was not the first 3-point attempt of Lively's rookie season, but his most recent one was exactly seven months earlier. He let it fly from the corner on Nov. 3 against the Denver Nuggets and Nov. 14 against the New Orleans Pelicans. He missed both.

In Game 4 of the NBA Finals, though, Lively's shot was pure. He held his follow through as the ball fell through the net.

"I think people forget he's a rookie," Doncic told reporters. "He's a rookie doing this stuff. And he's been amazing the whole season. Just watching him grow was unbelievable. And it's fun having him out there with me. And calling him my teammate, it's unbelievable. And it's a privilege to have him. And he's 50% on the season, so he might as well keep shooting. He's 1-for-2, right?"

Informed that Lively was actually 1-for-3, Doncic said, "All right. He's 1-for-1, he's 100% in the playoffs."

Lively's long-range surprise made the Dallas bench go bananas and Boston Celtics star Jayson Tatum slump his shoulders. It also gave the Mavericks a 13-11 lead, which it would not relinquish. Dallas avoided a sweep with a 122-84 rout at American Airlines Center, and it led by as many as 48 points. Boston pulled its starters with more than three minutes remaining in the third quarter, down by 36.

Lively finished with 11 points and 12 rebounds, seven of them on the offensive glass, in 22 minutes. Immediately after the 3, he helped on a Jrue Holiday drive, recovered to contest Xavier Tillman at the rim, sprinted the the other way after the stop and slammed home an alley-oop from Kyrie Irving.

Less than a minute after that, Derrick Jones Jr. made a hanging, twisting, double-pump layup around Tatum. Before the first quarter ended, Josh Green had thrown down a putback dunk and P.J. Washington had made an above-the-break 3 in transition. Early in the second quarter, Dante Exum attacked the basket and scored in traffic, then cashed an open 3 from Doncic. Dallas' two stars shot a combined 1-for-14 from deep, but their teammates shot 14-for-23.

It was the kind of balanced performance that got the Mavericks to the Finals in the first place but had eluded them for the first three games of the series. They were disruptive defensively, dominant on the glass and found clean looks in transition. Doncic and Irving created most of the offense, as usual, but the supporting cast finished plays.

"When you're desperate, the ball starts to move, guys are not overthinking it," Dallas coach Jason Kidd told reporters. "Being able to make some 3s tonight from our role players [was] huge when you talk about D-Jones, Exum and then D-Live. Just understanding that's who we've been all season. We can shoot with the best of 'em, and tonight we displayed that."

Despite Boston's spacing, and despite its abundance of playmakers, the Mavericks were everywhere defensively. Lively and Daniel Gafford looked just as intimidating as they did in earlier rounds; the Celtics scored 26 points in the paint, their second-lowest total all season, and never found a rhythm with their drive-and-kick game.

'They did a great job flying around, [causing] indecision on whether to shoot it or drive, and their multiple efforts," Boston coach Joe Mazzulla said. "And I thought their 5 men did a great job protecting the paint. Whenever we went in for a layup, they had multiple guys contesting." 

Kidd said that Lively was "in the right spot" on that memorable play in the first quarter. "He can shoot," he said. "That's the next step for his development, is being able to shoot the 3." Kidd added that, while they primarily need Lively to hit the glass and play defense right now, he grew up shooting and handling the ball.

As long as the Celtics continue to leave him open in the corner, Lively said he will continue to "get 'em up, for sure." He pointed to the ceiling as he said Friday's 3 was for his mother, Kathy Drysdale, who died of cancer in April.

"She helped me make it," he said. "She's going to help me make a lot more. She helped me make at the free throw line. She helped me make reads. I'm just thankful for having Luka pass me the ball in that position. I'm happy I knocked it down. I just gotta be able to make the next one."