Westbrook made things official with a post on Instagram shortly after the news broke:
Meanwhile, ESPN.com's Royce Young noted Westbrook inked the lucrative contract on a rather interesting date:
Last August, one month after Kevin Durant announced his decision to sign with the Golden State Warriors, Westbrook agreed to a three-year extension with the Thunder that was essentially a two-year deal since he could opt out after the 2017-18 season.
Wojnarowski noted Friday that Westbrook now owns the "biggest total contract" in league history since there are six years and $233 million left on his deal.
Per ESPN.com's Darren Rovell, he will make $569,512 per game (before taxes) in the final year of his extension.
"Russell's commitment to the Thunder organization since its inception in 2008 has helped propel us to great heights and stare down great challenges over our first decade," general manager Sam Presti said in a statement, per the Norman Transcript's Fred Katz. "We are extremely fortunate to have an athlete, competitor and person such as Russell wear the Thunder uniform. To have him cement his legacy as a leader as we enter into our 10th season in Oklahoma City is extraordinary."
Westbrook also released a statement, which was relayed by Young:
While the threat of Westbrook following Durant out the door loomed for Oklahoma City, the team was in a stronger negotiating position this time around. By making the All-NBA First Team, Westbrook could receive a super-max deal from the Thunder, which was created by the most recent collective bargaining agreement.
For Thunder general manager Sam Presti, Westbrook's contract was a straightforward pursuit: Offer him the super-max extension, and he either signs it or he doesn't.
Presti also had some added negotiating power after he acquired Paul George and Carmelo Anthony in a pair of offseason trades to show Westbrook he was committed to engaging in an arms race with the Western Conference's elite contenders.
Those moves were key, too, because Westbrook appeared overburdened at times during the 2016-17 campaign.
The league's reigning MVP, Westbrook averaged a triple-double (31.6 points, 10.7 rebounds and 10.4 assists) and set an NBA record for usage rate (41.7 percent), per Basketball-Reference.com.
There's no question the Thunder's reliance on Westbrook backfired at times, especially during the postseason. Oklahoma City lost to the Houston Rockets in the first round in five games. During the series, Westbrook attempted 30.4 shots a game and shot 38.8 percent from the field.
The Thunder didn't exactly have an alternative, though. According to NBA.com, Oklahoma City was 12.2 points better per 100 possessions with Westbrook on the floor during the regular season, and the team had a minus-51.3 net rating in the 46 minutes he was on the bench during the playoffs.
As CBSSports.com's Matt Moore wrote in April, Presti built a good roster that was centered around two of the five best players in the league. Durant's departure, however, radically changed the franchise's outlook, throwing off what was a delicate balance.
But now that George and Anthony are in the fold, the Thunder should quickly move back into a tier of elite Western Conference title contenders as they attempt to give the Rockets and Warriors a run for their money.
Assuming the team's new star-studded triumvirate can propel OKC toward the title summit, Presti will enter next summer with a compelling pitch to make Anthony and George as he hopes to keep the team's core in tact for years to come.