LAS VEGAS — Steven Luevano retained his WBO featherweight title in a scintillating draw with Mario Santiago tonight, and Monte Barrett knocked out touted heavyweight prospect Tye Fields 57 seconds into the first round on the eventful undercard of David Diaz's bout with Manny Pacquiao.

Referee Joe Cortez also made a baffling decision to end Humberto Soto's 130-pound bout with Francisco Lorenzo, handing a disqualification victory to the bloodied, crumpling Lorenzo after claiming he had been hit by Soto while he was down in the fourth round.

Luevano and Santiago put on the undercard's top bout, with both fighters flooring each other early on before chasing each other into the ropes later. Santiago threw nearly 200 more punches, but Luevano connected on 34 percent of his blows, significantly more than Santiago.

"(Santiago) really controlled the early part of the fight with that jab, but I felt I was the stronger one in the second half," Luevano said. "He tried to take me out early, and I felt that I was going to be stronger toward the end of the fight, and I was. I'm still champion, but the record book should say 'W' instead of 'D.'"

Luevano, the good-natured southpaw champion from La Puente, Calif., struggled to keep his feet at times against Santiago, a stylish Puerto Rican prospect who took his only loss last July in a technical decision against veteran Hector Velazquez.

Both fighters were aggressive from the bell, and each scored a knockdown early in the second round. The fifth was electric, with Santiago battering the champion into the ropes, where he barely survived without collapsing.

Harry Davis inexplicably scored the fight 117-111 for Luevano, but Duane Ford favored Santiago 115-113. Dave Moretti's card was even, 114-114.

"I felt like I won the fight," Santiago said. "I was a lot stronger than he was. I don't know what the judges were looking at. It was my fight, and they took it away."

Barrett (34-6, 20 KOs), a 37-year-old former title contender, stunned the crowd and his opponent at the Mandalay Bay Events Center with a stirring opening-minute attack. Fields (40-2), a 6-foot-9 former college basketball player with his own title aspirations, got clocked by an overhand right that weakened his knees, and Barrett then dropped the 265-pounder abruptly to the canvas with a left hook.

Referee Kenny Bayless ended the fight with Fields staggering to stand, and the 6-foot-3 Barrett did a backflip to celebrate a career that's been revitalized after three straight losses from 2005-07, including unsuccessful title shots against Hasim Rahman and 7-footer Nikolai Valuev.

Barrett said he hit Fields with "everything. That's why they call me Two Guns. I was a desperate fighter. Desperate fighters do desperate things. This was my last hurrah."

The Queens, N.Y., native sparred with a 6-foot-6 partner to prepare for Fields, who has made a tidy living in Las Vegas beating up lightly regarded fighters at various second-tier casino venues.

Cortez's ruling for Lorenzo was baffling to most fans and ringside observers who watched Soto (43-7-2) dismantle the Dominican fighter over four rounds.

Lorenzo was bleeding profusely and collapsing to the canvas in his corner when Cortez tentatively attempted to step in late in the fourth. Cortez shied away from stepping in for some reason, but he finally stopped the bout when Lorenzo apparently kneeled down voluntarily as Soto took a swing — which barely grazed Lorenzo, according to ringside replays.

After a lengthy conference among ringside officials while Lorenzo rested on his back, blood streaming from his nose, the 9-to-1 favorite Soto was disqualified. Lorenzo then jumped up and raised his hands to celebrate his interim WBC super featherweight title, while Soto fumed and laughed in disbelief.

"I was going to let him take a knee, and that's when (Lorenzo) got hit behind the head," Cortez said. "I looked at the replay, and I had to disqualify him."

Lorenzo was booed and jeered as he left the ring.