Westbrook distributed six assists and Sefolosha finished with 20 points as the Thunder swept the Suns in a home-and-home series and improved to 4-0 against them this season.
Kevin Durant picked up 18 points and grabbed seven rebounds for Oklahoma City, which went 9-of-17 from 3-point range.
Markieff Morris was the only Suns player to reach double figures with 12 points as Phoenix was held to 33 percent shooting in losing for the seventh time in nine contests overall.
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