The Celtics, fuelled by 30 points from Derrick White, defeated Orlando Magic 103-86.
The Cavaliers, who beat out the Celtics for top seed in the Eastern Conference, downed Miami Heat 121-100 and the Warriors, with 31 points from Stephen Curry, fended off a late Houston surge to beat the Rockets 95-85.
Oklahoma City, who emerged as top seeds in the Western Conference with the best overall record in the league, seized a 1-0 lead in their best-of-seven first-round series in emphatic style.
The Thunder’s 51-point margin of victory was even more remarkable given that Thunder star Shai Gilgeous-Alexander had his statistically worst performance of the season – managing just 15 points, five assists and three rebounds.
But all of Oklahoma City’s starters scored in double figures with Jalen Williams providing 20 points along with six assists and Aaron Wiggins contributing 21 points off the bench.
The win was the fifth-largest ever in NBA playoff history and also a franchise record.
“We played to our identity,” Gilgeous-Alexander said. “It’s going to be the key to our success – just be true to who we are.”
Grizzlies star Ja Morant finished with 17 points and vowed Memphis – who battled through the play-in tournament – would bounce back.
“We’ll never play that bad again,” Morant said.
Things were more tense in the day’s other Western Conference battle in Houston, where the Rockets sliced a 23-point deficit to three midway through the fourth quarter before the Warriors pulled away again to win.
Curry shook off a slow start to connect on 12 of 19 shots from the floor, including five three-pointers. Jimmy Butler added 25 points, seven rebounds, six assists and five steals for the Warriors.
“Stayed in it,” Butler said. “Gave up a little run, but in the end we won.”
In Boston, star forward Jayson Tatum scored a modest 17 points and finished the game despite a frightening fall under the basket in the fourth quarter that left him nursing a sore right wrist.
Tatum rose for a dunk and crashed to the court after he was hit by Kentavious Caldwell-Pope – who was assessed a flagrant foul upon review.
The Celtics faithful at TD Garden were delighted to see Tatum make his first three-pointer of the night soon after, and Tatum said after the game his wrist was fine.
Jaylen Brown, back for the postseason after battling knee trouble, scored 16 points and Payton Pritchard added 19 off the bench for Boston, who trailed by one after a nip-and-tuck first half but pulled away relentlessly after the break.
“Just a good response there in the second half,” said White, who had seven of the Celtics’ 16 three-pointers.
Paolo Banchero scored 36 points and grabbed 11 rebounds for the Magic. Franz Wagner added 23 points but no other Orlando player scored in double figures.
In Cleveland, Donovan Mitchell scored 30 points and Ty Jerome added 16 of his 28 in the fourth quarter as the Cavaliers finally put away the determined Heat.
Miami, who advanced from the play-in tournament on Friday, trailed by 16 in the second quarter, but kept chipping away and were down by just eight midway through the fourth quarter.
Jerome, in his first playoff game, caught fire, making six of his seven shots in the final period to help Cleveland pull away for good.
“The thing that makes us special – it can be anybody any night,” Mitchell said, but added that plenty of work remains.
“We didn’t accomplish anything,” Mitchell said. “We just took care of our first job at home.” (AFP)
