Nate Campbell insisted the bloody cut on his injured eye resulted from an accidental head-butt. Timothy Bradley thought it had more to do with the dozens of punches he threw in just three dynamic rounds.

Although the cut's origin is still under debate, it resulted in a major victory for the hometown fighter.

Bradley defended his WBO 140-pound title Saturday night by battering Campbell, whose eye injury stopped the fight before the fourth round.

"I was just doing my job," Bradley said. "(The injury) didn't matter anyway. He was getting older and older through the fight. I was beating him easily."

Bradley (25-0, 12 KOs) rode the energy of his Palm Springs-area crowd in an aggressive, active performance. Campbell, the 37-year-old veteran, claimed the only blow that did irreparable damage was from an accidental head-butt early in the third.

Campbell (33-6-1) thought the fight therefore should have been ruled a no-contest, and promoter Don King joined him in howling at the injustice.

"A cut like this comes from a head-butt," Campbell said. "That was no punch. The California commission is wrong. This is just wrong. You can see it on television. How can they deem it a TKO? All they have to do is watch and see that it was a head-butt. This is not right."

The head-butt was obvious on television replays, but its relationship to the cut wasn't clear. Campbell's eye also was injured in the round, which he barely survived on his feet.

Referee David Mendoza didn't buy Campbell's claim, awarding a TKO to Bradley, who made his first defense of the light welterweight belt he claimed from Kendall Holt in April.

"They were both butting each other all night," Mendoza said. "The last one was a head-butt, but the blood came after the punch, not from the head-butt. That's what I saw last: The punch, then the blood."

The loss is another twist for Campbell, who had fought just once since his stunning victory over Juan Diaz in Cancun in March 2008 to win three lightweight belts. He lost one big payday when Joan Guzman couldn't make weight to face him, and Campbell then failed to make 135 pounds himself, pushing him to move up to 140.

He taunted Bradley before the fight, but didn't appear to have the speed to keep up with Bradley's busy fists.

"Nate showed his face, and I was victorious," Bradley said. "I just attacked."

Campbell insisted he should get another shot, which Bradley and promoter Gary Shaw said they wouldn't mind, with Bradley labeling it "easy money."

Aside from the debatable ending, the evening went almost perfectly for Bradley, who gave up his WBC 140-pound belt so he could take on Campbell. Bradley declined to fight mandatory WBC challenger Devon Alexander, who won that vacant belt by beating England's Junior Witter earlier at the Agua Caliente Casino Resort.

The casino is just outside of Palm Springs, and 2,289 of Bradley's home fans turned out in emphatic support of the 25-year-old champion, filling the arena with raucous chants and cheers. Bradley gave a crowd-pleasing effort, peppering Campbell with dozens of punches while chasing the older challenger around the ring.

The 22-year-old Alexander won his first world title when Witter quit before the ninth round, citing a hand injury. Alexander (19-0, 12 KOs) largely dominated the bout, and wept when he raised the belt.