LAS VEGAS (AP) -- Middleweight champion Anderson Silva stopped Chael Sonnen at 1:55 of the second round in UFC 148 on Saturday night at the MGM Grand Garden Arena.Silva has successfully defended his title 10 times and had a 15-match winning streak.In the second round, Sonnen fell to the canvas and up against the fence after missing with a wild spinning backfist and Silva capitalized, landing a knee to the chest and then a number of solid strikes, forcing the referee to stop the fight. The fight was a rematch of the 2010 fight of the year, where Sonnen dominated Silva for 4 12 rounds before losing by submission.On Saturday night, Sonnen had an early takedown and kept Silva on the mat for almost the entire first round, easily winning the round on the scorecards.Sonnen looked to take Silva down again in the second, pressing the action and forcing Silva up against the cage. The two separated and moved across the octagon, but Sonnen's miscue led to his quick demise.Earlier, Forrest Griffin edged Tito Ortiz in a close unanimous decision in a bout matching former light heavyweight champions.Griffin was able to land a number of kicks to the legs and body and controlled most of the fight that ended with three judges giving him a 29-28 edge. Ortiz rocked Griffin in the second and third rounds, flooring him with right hands, but Griffin rallied to sustain the attack.On the undercard, Cung Le unanimously outpointed Patrick Cote for his first UFC victory, Damian Maia stopped Dong Hyun Kim in the first round, Chad Mendes rebounded from his first loss with an easy first-round victory over Cody McKenzie, and D.C. native Mike Easton outpointed Ivan Menjivar, winning by unanimous decision.In the preliminary bouts, Melvin Guillard earned his 11th UFC victory, and Khabib Nurmagomedov remained undefeated at 18-0, both winning unanimous decisions. Rafaello Oliveira, Shane Roller and Costa Philippou also won by unanimous decision.