CARSON, Calif. -- Nonito Donaire knew he had nearly an impossible act to follow. Right before he took the ring, Brandon Rios and Mike Alvarado brawled through arguably the most sensational fight of the year.
Donaire did his best to provide his own thrills, and he eventually finished off another tough opponent on an impressive list.
Donaire stopped Toshiaki Nishioka at 1:54 of the ninth round Saturday night, defending his WBO 122-pound title with a dominant performance in his 29th straight victory.
But fans at the sold-out Home Depot Center booed much of the champion's win because of what happened right before it.
Rios stopped Alvarado in the seventh round of a sensational 140-pound bout in the co-main event. Both previously unbeaten fighters absorbed enormous punishment and rallied tenaciously in a fight compared to Ali-Frazier, Hagler-Hearns and Corrales-Castillo by promoter Bob Arum.
"This really exceeded what I thought," Arum said. "These two guys stood in the center of the ring. They didn't clinch once. They threw every punch they had at each other, and until one guy went down and the referee stopped the fight, you didn't know who was going to win. That was a really classic, great fight."
Donaire (30-1, 19 KOs) was less thrilling but more dominant, patiently waiting for openings against Nishioka (39-5-3) before knocking down the Japanese veteran in the sixth despite hurting his left hand during the bout, opening a huge cut on his knuckle.
Donaire, the Filipino-born champion raised in California's Bay Area, then put him down again with a vicious right hand in the ninth, and referee Raul Caiz stopped it after Donaire landed an uppercut moments later. Nishioka had won 16 straight fights since March 2004, including a win over Rafael Marquez last year, but couldn't keep up with Donaire's combination of power and tactical skill.
"I was just playing possum to see what he'll do," Donaire said. "I wanted to open him up and time the jab, and that's exactly what happened."
Nishioka threw just eight punches in the first round. Donaire attempted to force the action with little success until the sixth, when he landed a left uppercut, followed by a right hand and another uppercut that put Nishioka on the canvas.
"When you do engage, you open up yourself," Donaire said. "Nonito is a surgeon. I can pick them apart, and then the demolition comes later."
Donaire, who also held the IBF version of the 122-pound title before vacating it this week, was upstaged by Rios and Alvarado in a fight that thoroughly lived up to its hype.
Rios (31-0-1, 22 KOs) and Alvarado put on a show for the packed arena, trading hundreds of big shots and largely ignoring defense. Both fighters are known as heavy-handed brawlers, and both stayed on their feet during 6½ rounds of bombardment, starting with a frenetic first round in which both fighters landed numerous devastating blows. The left side of Alvarado's face began to swell, and Rios took damage all over his face.
Rios, the Kansas-raised former lightweight champion, ate dozens of powerful shots from the Denver-based Alvarado (33-1) in the fifth and sixth rounds.
Alvarado threw 147 punches in the fifth round alone -- but Rios abruptly landed a devastating overhand right that rendered his opponent defenseless in the seventh. Alvarado took several additional shots before referee Pat Russell stepped in with Alvarado backed against the ropes.
"It was a really tough fight, but I could have gone a little longer," Rios said. "He tested my chin, and I handled it. I am a warrior. He didn't hurt me. He got me a little stunned, but I was ready to go on."
Alvarado threw 238 more punches than Rios, but the winner connected with a much larger percentage of total blows. Rios landed 33 percent of his 440 power punches, while Alvarado connected with 31 percent.
Alvarado thought Russell had stopped the fight too early, but complimented Rios' toughness.
"He shook me up a little bit, but I could have kept fighting," Alvarado said.
Arum had said the winner of this bout would be considered as Manny Pacquiao's next opponent, but both Rios and Alvarado said they were open to a rematch.