Jaylen Brown opened the Eastern Conference semifinals with a team-best 29 points Tuesday night. But it wasn’t his name the TD Garden crowd was chanting.

It wasn’t Jayson Tatum’s, either. His unimpressive double-double didn’t measure up to his usual All-NBA standards.

No, it was the former role player who doused Miami Heat with 3-pointers to close out the opening round of the NBA playoffs, then did the same in Game 1 against the overmatched Cavaliers.

“Der-rick White. Der-rick White.”

That’s what Celtics fans bellowed in unison as White drained seven threes to help lead Boston to a 120-95 win and a 1-0 lead in the best-of-seven series. Game 2 is Thursday night on Causeway Street.

White finished with 25 points on 9-of-16 shooting (7 of 12 from three). Brown was an efficient 12-for-18 (4 of 6), while Tatum finished with 18 points, 11 rebounds, five assists and three blocks.

Cavs All-Star Donovan Mitchell gave the Celtics problems with 33 points (12 of 25; 4 of 11 from three), but the rest of Cleveland’s roster shot just 38.5% from the floor and 22.6% on threes.

As was the case in last week’s Game 5 clincher against Miami, Brown was Boston’s offensive catalyst in the opening minutes. He opened the scoring with a 3-pointer, drew fouls down low on two of the next three Celtics possessions, then nailed a tough floater over Mitchell as part of a 15-point first quarter.

Brown did not miss from the floor (where he started 5-for-5) or the line (4-for-4) until the closing seconds of the quarter, when his heave from halfcourt bounced off the rim.

Nineteen of the Celtics’ first 21 points came from either Brown or White, whose first three prompted Cavs coach JB Bickerstaff to call his first timeout less than four minutes after tipoff.

White’s emergence as a lethal 3-point sharpshooter has added yet another weapon to Celtics offense that ranked second in scoring during the regular season. The 29-year-old made at least five threes in each of Boston’s last three games — the first time he’d done so in his NBA career.

Cleveland settled in after the stoppage, making eight of its next 10 shots (including four threes) to take a 23-21 lead and trigger a Joe Mazzulla timeout. The Celtics wound up scoring 40 first-quarter points (their third-most this postseason) but allowed 34 (their second-most).

A slower second quarter ensued, and Boston took a 59-49 lead into the locker room, but a shift in Cleveland’s strategy. The Cavs made as many 3-pointers in the first half (eight) as they did in all of Game 7 of their first-round series against Orlando, and they attempted nearly as many (22 compared to 24).

That’s the blueprint the Heat used to hand the Celtics their lone loss of Round 1. But much like Miami’s plan, it proved unsustainable. Cleveland went 2-for-30 on threes after halftime and scored just 55 points over the final three quarters.

Both teams were missing key frontcourt pieces Tuesday night, with Kristaps Porzingis (calf strain) unavailable for the second consecutive game and Jarrett Allen (bruised ribs) sitting out his fourth straight.

For Cleveland, playing without Allen meant a smaller starting five — 6-foot-5 Isaac Okoro replaced the 6-11 center — and early minutes for a couple of aging former Celtics. Marcus Morris and Tristan Thompson both subbed in before the end of the first quarter, with Thompson drawing boos from the Garden crowd.

The Celtics stuck with Al Horford as their starting big in place of Porzingis and got an unexpectedly impactful performance from his backup, Luke Kornet.

The 7-foot-2 reserve matched his playoff career high for rebounds before halftime, blocked two shots, forced misses by Mitchell and Evan Mobley with tight defense, and dished a slick pass to Tatum for an easy layup. Kornet also threw down a rim-rocking dunk late in the third quarter and set a postseason personal best for minutes played with 21.

Mazzulla briefly expanded his rotation when he inserted trade-deadline pickup Xavier Tillman to start the second quarter. But Tillman — who only saw the floor in garbage time against Miami — was lifted after just four minutes and didn’t reenter until late in the fourth.

Backup point guard Payton Pritchard started 1-for-6 from deep but hit three triples in the second half — including one from just inside the logo at the third-quarter buzzer — to help Boston pull away.