But their friendship takes a back seat when they step on the court this week. At least in Westbrook's eyes.
"When I get on the floor, I got one friend, and that's the basketball," Westbrook said before the Thunder's 118-87 loss to the Rockets in Game 1 of their Western Conference playoff series. "I've been like that since I was a little kid. My dad told me that when I was younger: 'You got one friend, and your friend is Spalding. At the time maybe it was Wilson or some other s---.'
"Whatever the ball is, that's who my friend is."
Harden and Westbrook knew each other growing up in Los Angeles and played at the same Boys & Girls Club. They text and talk often during the season. It was Harden who ran over to Westbrook at the All-Star Game in New Orleans when he warmed up on a different basket than former teammate Kevin Durant.
"Since 10 years old. That's never gonna change," Harden said Sunday morning of his friendship with Westbrook after the Rockets' shootaround.
"When I get on the floor I got one friend, and that's the basketball."Russell Westbrook
Westbrook and Harden are leading MVP candidates this season. The results of that voting won't be known until after the postseason, when the awards are presented at the first "NBA Awards Show" on TNT in New York on June 26.
"I don't want to talk about that," Harden said of the MVP race. "I'm focused on the playoffs. ... That's the most important thing."