Unbeaten Mexican star Julio Cesar Chavez Jnr kept his World Boxing Council middleweight crown by stopping US challenger Peter Manfredo in the fifth round. Chavez landed a stunning right to Manfredo's head and followed with 30 unanswered punches as the American tried in vain to evade the champion's blows before referee Laurence Cole halted the bout one minute and fifty-two seconds into the fifth round. "I've been working at it a lot, trying to box instead of fight. It took me a while to get into it but it worked out well," Chavez said. "In the long run we were going to fight, we were going to roll." The son of legendary fighter Julio Cesar Chavez improved to 44-0 with one draw with his 31st victory inside the distance, the first defense of the title he won last June with a 12-round decision over Germany's Sebastian Zbik. Manfredo fell to 37-7, ending a six-fight win streak in what he said might have been his final bout. "It didn't go my way. But he caught me with a good shot. He won," Manfredo said. "I'm trying to make him miss, trying to grab on, but (the referee) stopped it." Chavez, the larger fighter, connected on solid power punches throughout the second round and both men landed solid straight right hands to the head in the third. Manfredo bloodied Chavez's nose in an aggressive fourth round performance but Chavez responded in the fifth with his stunning blow and pressed the attack to the finish. Chavez, whose strong support from Mexican fight fans makes him the top moneyspinner in his weight class, said he has no preference regarding his next opponent. "I want to fight the best," he said. "I fear no one."