The Rockets have recently acquired All-Star MVP Russel Westbrook. The Rockets traded CP3 for Russell Westbrook and multiple first round picks according to Adrian Wojnarowski.
Below is the tweet from Adrian Wojnarowski. The Rockets gave up future first round picks, but for a contending team, these may not be much in the future.
Russell Westbrook and James Harden go back to OKC, where Harden was the 6th man. They have remained close friends since, and this move will certainly please Harden.