The Celtics kicked off their longest road trip of the season by routing one of the NBA’s worst teams Friday night.

Playing without an injured Jaylen Brown, Boston withstood a spirited upset bid by the tanking Utah Jazz to win 121-99 night at the Delta Center.

Kristaps Porzingis (27 points, 10 rebounds, six assists) and Jayson Tatum (26 points, six rebounds, six assists, three steals) delivered standout performances for the Celtics, who extended their winning streak to four games. Payton Pritchard and Sam Hauser hit four 3-pointers apiece and combined for 32 points off the bench, while fellow reserve Luke Kornet grabbed eight rebounds, blocked three shots and finished as a game-best plus-23.

Colin Sexton scored 30 points to lead the talent-deficient Jazz, who trailed by single digits midway through the third quarter before Boston pulled away late.

The Celtics, winners of nine of their last 10, improved to 51-19 with 12 games remaining. The Jazz fell to 16-55.

Tatum, who sat out Tuesday’s victory over the Brooklyn Nets with a knee injury, shredded the Jazz during a dominant first quarter, scoring 14 points on 6-of-9 shooting while dishing out three assists. He was highly active on the defensive end, too, with three rebounds, three steals and a blocked shot.

During one especially impressive sequence, Tatum stole a Utah pass, ran the floor, briefly lost control of the ball, inadvertently kicked it back to himself and finished at the rim.

That was one of the few unassisted baskets the Celtics had in the first half. They assisted on their first seven makes and 14 of their first 18. Those 14 included four 3-pointers off offensive rebounds — one each by Hauser and Pritchard and two by Porzingis.

Porzingis has not looked at all rusty since returning from the viral illness that sidelined him for eight straight games. After scoring 25 and 24 points in Boston’s two wins over Brooklyn this week, the center topped 20 before halftime Friday. His 21 first-half points (on 6-of-12 shooting) were his second-most in a Celtics uniform.

Utah outscored Boston in the second quarter, however, and trailed by single digits at the half, 60-51. Walker Kessler aided that upset effort with six offensive rebounds and a loud rejection of a Tatum dunk attempt, and the Jazz got 19 first-half points and five 3-pointers from their bench.

Three Sexton treys early in the third quarter cut the deficit to four. Porzingis also picked up his third and fourth fouls in quick succession midway through the third, sending him to the bench and Kornet back onto the court for the first time since the first quarter. A Keyonte George three moments later trimmed Boston’s lead to 71-69.

But the Celtics responded with a three from Tatum and Derrick White’s third steal of the game, which led to a fast-break layup by Kornet. Boston then got two Hauser threes bookending a steal and transition dunk by Tatum. That 13-0 run put the Celtics ahead 84-69, and they led comfortably the rest of the way.

“Sexton played great,” Celtics head coach Joe Mazzulla told reporters. “They got off to a really good start to start the third quarter. I just thought we needed to take it to another level, and credit to the guys. They took it to another level and they got some live-ball turnovers, got out in transition, got some stops. I thought each guy was good throughout most of the game of just kind of their activity and making plays for each other on both ends.”

Jrue Holiday helped Boston maintain that lead with a succession of hustle plays. After Utah cut it to 10, the veteran guard foiled a scoring chance with a leaping interception, then scored on a give-and-go layup from Porzingis at the other end. Holiday then assisted on a Porzingis jumper and sank one of his own on the next Celtics possession.

After Boston successfully challenged a defensive foul on Baylor Scheierman — his dunk contest was deemed legal, resulting in a Utah turnover — Pritchard quickly poured in eight points, including a pair of deep threes, to make it 105-87 with 7:08 remaining.

The Celtics totaled 13 steals and four blocks against a Utah team that ranks last in the NBA in turnover percentage.

Mazzulla sent in his subs in the final minutes, closing the game with Scheierman, JD Davison, Jordan Walsh, Drew Peterson and Neemias Queta. Walsh delivered two putback dunks, and two-way player Davison tallied four points and three rebounds in his three minutes of floor time.

The Celtics’ road trip continues Sunday in Portland, then heads to Sacramento on Monday, Phoenix on Wednesday and San Antonio next Saturday before wrapping up in Memphis on Monday, March 31. Of those teams, only the Grizzlies are close to contention, entering Friday two games back of second place in the Western Conference.

The Jazz, Trail Blazers, Kings, Suns and Spurs occupy five of the bottom seven spots in the West standings.

Off the rim

The Celtics also ruled Brown (bone bruise with posterior impingement in his right knee) out for Sunday’s matchup with the Blazers. He will be reevaluated on Monday. After that evaluation, Brown must play in at least nine of Boston’s final 11 games to qualify for All-NBA and All-Defensive team consideration. … Porzingis and Sexton briefly scrapped after a fourth-quarter whistle, resulting in technical fouls on both players. … Scheierman went scoreless (0-for-3) after his 20-point eruption Tuesday night, but his strong rim contest helped Boston maintain its late-game momentum. The rookie also drew an offensive foul earlier in the night.