NEW YORK (AP) Jayson Tatum was stunned, yet certain. He disagreed with his sixth foul but had no doubt the Boston Celtics, with their rock-solid defense, would hold on without their scoring star.

''Couldn't believe it at all, but I think that's what we're built for,'' Tatum said.

They might be built for a championship.

Tatum scored 29 points, Jaylen Brown had 22 and the Celtics completed a four-game sweep of the Brooklyn Nets, becoming the first team to reach the second round of the playoffs with a 116-112 victory Monday night.

Marcus Smart added 20 points and 11 assists for the No. 2-seeded Celtics, who made easy work of what was thought could be a tough series. Boston will wait for the winner of the series between Milwaukee and Chicago, where the defending champion Bucks hold a 3-1 lead.

The Celtics showed no fear of the Nets, who with Kevin Durant and Kyrie Irving didn't have the profile of the typical low seed. Boston won on the final day of the regular season instead of losing to fall down the standings and avoid the matchup.

Turns out, there was no reason to worry.

''It's funny to us, because we don't duck and dodge anybody,'' Smart said. ''We knew what we were going to come in here and do.''

Durant had 39 points, nine assists and seven rebounds, breaking free after the Celtics had defended him well in the first three games. But he couldn't get the Nets the win they needed to extend what instead goes down as a massive failure of a season.

Expected to be an NBA Finals contender, the Nets needed a strong finish just to grab the No. 7 seed.

Seth Curry scored 23 points for the Nets. Irving, whose unavailability for home games much of the season because he isn't vaccinated against the coronavirus contributed to the Nets performing so far below expectations, had 20 points.

''A lot of stuff that may factor into why we lose, but they were just a better team,'' Durant said.

The Celtics were under .500 at the midpoint of their season but went 31-10 from there, with Tatum emerging as the potent scorer on one of the NBA's best defensive teams.

That defense limited Durant to just 19-for-52 shooting with 17 turnovers through the first three games and made it tough for him, even as he finally got more shots to drop Monday. He was only 13 of 31 from the field, 3 for 11 behind the arc.

He lost in the first round for the first time since 2010 with Oklahoma City, the first playoff series of his career. He had won nine straight first-round series.

Tatum had 12 points in the third quarter and the Celtics opened a 90-75 lead in the closing seconds of the period. But he went to the bench with a fifth foul with 8:17 remaining and the Nets made a push that got them within three points about three minutes later.

Tatum fouled out with the Celtics leading by six with 2:48 to play. Irving made a 3-pointer and Durant scored to cut it to 109-108 with 1:28 remaining. But after a basket by Brown, Durant could only make one free throw and the Celtics rushed down the floor, with Al Horford putting back Smart's miss to make it 113-109 with 13 seconds left.

With Durant, Irving and James Harden, the Nets began the season as a team that looked potent enough to win their first NBA title. But Irving didn't play at all to begin the season, and not long after he came back playing road games only, Harden became unhappy and the Nets dealt him to Philadelphia in a trade for Ben Simmons.

The Nets hoped they could have Simmons make his debut for them in Game 4, but he was ruled out Sunday with more pain in his back that has troubled him since not long after arriving in a midseason trade with Philadelphia.

Irving said his emotions were ''disappointment, a little sadness, because we didn't play as well as a team as we wanted to.''

The Nets were down only 45-44 with 3:29 to play in the second quarter. But Grant Williams made three 3-pointers from then until the end of the half, with the final one giving Boston a 58-50 lead.

TIP-INS

Celtics: Boston swept its first-round series for the third time in four years. The Celtics beat Indiana in four games in 2019 and Philadelphia in 2020 at Walt Disney World. They lost 4-1 in the first round to the Nets last season. . Williams scored 14 points and Horford had 13.

Nets: Bruce Brown scored just two points after having 26 and 23 in the previous two games, the first time he had consecutive 20-point games in his career. . Nic Claxton scored 13 points. He was 6 for 6 from the field but 1 for 11 at the free throw line, missing his first 10 before making the last one when the Celtics fouled him intentionally.

SIMMONS SITUATION

Coach Steve Nash said he didn't want to speak for Simmons, but acknowledged there was a mental side beyond the physical problems he is facing. Simmons cited mental health concerns as a reason he sought to leave Philadelphia and didn't suit up for the 76ers this season.

''I think Ben has addressed that there is a mental component with what he's going through, but how much and where he's at with that is not for me to speak about,'' Nash said. ''But as far as an organization, we're really pushing to support Ben in any way we can to help him improve physically and get back on the court, and then the mental side of that is part and parcel. They're not separate, they're not something that we don't want to deal with. We want to help if he needs help in any aspect of his life and his game.''

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