Westbrook finished with 15 points, 15 assists and 13 rebounds. He now has the longest triple-double streak of his career and is one short of Wilt Chamberlain's NBA record of nine straight set in 1968.
Paul George scored 27 points and Jerami Grant added 20 for Oklahoma City, which has won nine of 10.
Jaren Jackson Jr. scored 27 points for the Grizzlies, who were reeling from the news that franchise cornerstone Marc Gasol was traded to the Raptors for three players.
The Grizzlies also announced Thursday that they sent JaMychal Green and Garrett Temple to the Los Angeles Clippers for Avery Bradley. There were only 11 players in uniform for the Grizzlies, and eight played.
Memphis led 53-51 at halftime before the Thunder found their groove.
Oklahoma City center Steven Adams stole the ball and drove nearly the length of the floor for a layup to put the Thunder ahead 57-55. Adams was scoreless in the first half, but he had nine points in the third quarter to help Oklahoma City take an 83-72 lead. The Thunder scored the first 11 points of the fourth quarter to put the game out of reach.
Grizzlies: Fell behind 7-0 to start the game. ... C Ivan Rabb started for the second time this season. He had 15 points and nine rebounds. ... Coach J.B. Bickerstaff was called for a technical in the second quarter.
Thunder: George and Westbrook will play together on Team Giannis at the All-Star Game. Westbrook was traded from Team LeBron for Philadelphia's Ben Simmons. ... G Alex Abrines missed the game for personal reasons. ... Westbrook has 21 triple-doubles this season and 125 in his career.
Grizzlies: Host the New Orleans Pelicans on Saturday.
Thunder: Visit the Houston Rockets on Saturday.
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