Viloria, 25, turned in one of his worst performances as a professional and the judges agreed by unanimously scoring the 12-round fight 117-112, 118-110 and 117-111 in favor of Nino.

"I knew if he was going to beat me he was going to have to hit me with counters and as long as I kept my jab out there, he wasn't going to counter anything," said Nino, 30, of Guadalajara, Mexico, who outlanded Viloria 245-113 and outpunched him 778-398.

Viloria, a 2000 U.S. Olympian, landed several hard right hands early, but was never able to put more than one punch together at a time.

After the fourth round, Nino took control, rarely allowing the hard-hitting Viloria to land one of his big shots.

Viloria (19-1) had been hoping to arrange a big-money fight with popular WBA champion Koki Kameda.

"It just wasn't my night," Viloria said, shrugging. "I knew what was on the line. I just had a bad night. I'm not going to make excuses. I just had a bad night."

It was made much worse by Nino (24-2-1), who said he was convinced early that he would win the title. Though Nino knew he was only brought in to be the opponent to showcase Viloria, he said losing never entered his mind.

"I came here with one thing on my mind and that was winning the title," Nino said. "I wanted this more than anything and I was going to get it.

"I heard he was a hard hitter, but I felt his power early and he never hurt me. That's when I knew I had him."