Sergio Martinez dominated for 11 rounds, then escaped a manic 12th by Julio Cesar Chavez Jr. to take the WBC middleweight belt.
In the end, Martinez (50-2-2) took a 118-109, 118-109 and 117-110 decision, but it was the final round that proved most memorable.
There, a bloodied Chavez (46-1-1) managed to send Martinez to the canvas with a flurry of left hooks. Martinez staggered to his feet, but was knocked down again in the round and was taking a heavy beating when the bell marked the end of the fight.
Also on Saturday, Roman Martinez defeated Miguel Beltran in a split decision at the Thomas & Mack Center to capture the vacant WBO super featherweight belt.
Martinez (26-1-1) held the slight edge on the scorecards with a pair of 114-113 rulings while one judge had Beltran (27-2) up 116-111.