The Oklahoma City Thunder have sent a clear message to NBA playoffs rivals rivals in their opening game, crushing the Memphis Grizzlies 131-80 - the fifth-biggest margin of victory in postseason history.

The 51-point margin in their western conference first-round opener at home on Sunday was seven points shy of the record and was the largest Game 1 win in NBA playoff history.

Aaron Wiggins scored 21 points, Jalen Williams scored 20 points and Chet Holmgren had 19 points and 10 rebounds for the top-seeded Thunder, who finished the regular-season with a league-best 68-14 record.

Shai Gilgeous-Alexander, the league's scoring champion with nearly 33 points per game, scored just 15. The Thunder still shot 50.5 per centfrom the field.

"We played to our identity," Gilgeous-Alexander said. "Nothing more, nothing less than that. We were who we were all year ... and it's going to be the key to our success, just staying true to who we are."

Gilgeous-Alexander had said several times since Oklahoma City's loss to Dallas in last season's western conference semi-finals that he would be intentional about getting his teammates better prepared for this postseason.

"I have a great group of guys around me, and I know that," Gilgeous-Alexander said. "And I've known that for a long time. ... They obviously played amazing."

Ja Morant scored 17 points for Memphis on just 6-for-17 shooting. Jaren Jackson Jr., who averaged just over 22 points in the regular season, scored four points on 2-for-13 shooting. The Grizzlies shot just 34.4 per cent overall.

In the eastern conference, top seeds Cleveland also began their playoffs campaign with a strong win, defeating the Miami Heat 121-100 at home.

Donovan Mitchell scored 30 points, Darius Garland had 27 and Ty Jerome had 16 of his 28 points in the fourth quarter for the Cleveland Cavaliers.

It was the seventh straight series where Mitchell has scored at least 30 points in Game 1, tying Michael Jordan, who had two streaks of seven games.

Bam Adebayo had 24 points and Tyler Herro added 21 for the Heat, the first No. 10 seed to advance to the playoffs out of the play-in tournament.

In Boston, the defending champion Celtics dominated to beat the Orlando Magic 103-86 in Game 1 of their eastern conference first-round series, with Derrick White scoring 30 points and Jayson Tatum finishing the game with 17 after a scary fall.

In Houston, the Golden State Warriors showed they remain a potent threat behind the talents of Stephen Curry and Jimmy Butler, beating the second-seeded Houston Rockets 95-85 in their western conference series opener after advancing from the play-in tournament.

Curry had 31 points and star late-season arrival Butler added 25 points seven rebounds, six assists and five steals.

Australian centre Jock Landale was unused by the Rockets who got 26 points and nine rebounds from starting centre Alperen Sengun and 12 rebounds from Kiwi big man Steven Adams.