Chael Sonnen shared his theory on why Anderson Silva failed his drug test.

EXCLUSIVE: Chael Sonnen gives his thoughts on Vitor Belfort taking on Jon Jones at UFC 152 and updates Dan Henderson's injury.

Watch complete fight videos from Anderson Silva title defenses, including his victories over Chael Sonnen (UFC 117), Dan Henderson (UFC 82), Vitor Belfort (126), and Yushin Okami (UFC 134).

Watch the complete first episode of the UFC 148: "Silva vs. Sonnen 2" Primetime series that goes behind the scenes of the big Middleweight championship fight pitting Anderson Silva vs. Chael Sonnen.

As expected, Hector Lombard has opened as a heavy favorite in his UFC debut fight against Tim Boetsch at UFC 149 on July 21 in Calgary, Alberta, Canada.