LAS VEGAS -- Sharmba Mitchell didn't need open scoring to know he was winning his fight. All he had to do was look at his opponent's face.

Mitchell defended his WBA super lightweight title for the fourth time Saturday night, overcoming a sixth round head butt to win a unanimous decision over a bloodied Elio Ortiz of Venezuela.

The bout was on the undercard of the Evander Holyfield-Lennox Lewis heavyweight unification fight at the UNLV campus arena.

It was the first title defense for Mitchell since he beat Reggie Green on April 24 in a bout that was a test of open scoring in which the scores of the three ringside judges were announced after each round.

Mitchell used that information to his advantage against Green by staying away in the final round, knowing Green needed a knockout to win.

Against Ortiz, though, it wasn't necessary.

Mitchell knocked the challenger down with a right-left combination in the first round and opened a cut over his right eye two rounds later. By the middle rounds, the challenger's left eye was almost swollen shut and Mitchell cruised to the win.

"I don't get any slouches. That's why I'm the best pound for pound fighter in the world," Mitchell said.

Mitchell said the head butt, which caused blood to flow into his right eye, bothered him, although he continued to batter Ortiz as the fight ended.

"It really didn't bother me at first, but in the later rounds I really couldn't see out of my right eye," Mitchell said.

Mitchell, 139½ pounds, of Takoma Park, Md., improved to 46-2 in a fight that paid him $100,000. He hasn't lost since dropping two consecutive fights in 1994.

Ortiz, also 139½, was the WBA No. 3 contender. He fell to 17-4.

Two other WBA title fights were also on the card.

France's Fabrice Tiozzo defended his WBA cruiserweight title against Ken Murphy of Chicago, while Gilbert Serrano of Venezuela took the WBA lightweight title from Italy's Stefano Zoff.

Tiozzo, 189½, got little more than a workout against Murphy, who was ranked No. 12 by the WBA and was overmatched against the champion.

Tiozzo dropped Murphy late in the seventh round with a right hand, although he got up and finished the round. But referee Joe Cortez stopped the fight with Murphy back on his corner stool after the end of the seventh round.

Tiozzo improved to 41-1 while Murphy, 188, dropped to 21-2-1. Tiozzo earned $50,000 to $35,000 for Murphy.

Zoff was cut over the right eye during his fight with Serrano, and referee Jay Nady finally stopped the bout at 31 seconds of the 10th round on the advice of the ringside physician.

Serrano, 134, who was the No. 1 contender, improved to 18-4-2. Zoff, 133½, fell to 29-7-2.