OKLAHOMA CITY — The Oklahoma City Thunder beat the Memphis Grizzlies 131-80 in Game 1 of their first-round Western Conference playoff series on Sunday, the fifth-biggest margin of victory in NBA postseason history.

The 51-point margin was seven points shy of the record and was the largest Game 1 win in NBA playoff history.

Jalen Williams scored 20 points and Chet Holmgren had 19 points and 10 rebounds. Shai Gilgeous-Alexander, the league’s scoring champion with nearly 33 points per game, scored just 15. The Thunder still shot 50.5% from the field.

Oklahoma City, which finished the regular-season with a league-best 68-14 record, looked every bit the part of an overall No. 1 seed.

There have been two 58-point playoff margins in NBA history: Denver beating New Orleans 121-63 in 2009 and the Minneapolis Lakers beating the St. Louis Hawks 133-75 in 1956.

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. Marvin Bagley III also scored 17, but the Grizzlies shot just 34.4% overall.

This was Memphis’ first playoff game under interim coach Tuomas Iisalo. He coached just nine NBA regular-season games before the play-in games.

The Los Angeles Lakers beat Golden State by 56 (126-70) in 1973 and the Chicago Bulls beat the Milwaukee Bucks by 54 (120-66) in 2015. And now, a 51-point game — where the Thunder had it well in hand by early in the second quarter. They took a 35-point lead into halftime.

Game 2 is Tuesday.

Oklahoma City Thunder forward Jalen Williams dunks as Memphis Grizzlies forward Jaren Jackson Jr., right, looks on during the first half in Game 1 on Sunday. Nate Billings / AP

The Associated Press