CARSON, California (AP) — Rising welterweight Keith Thurman remained unbeaten Saturday night, stopping Julio Diaz after three rounds when Diaz's corner threw in the towel due to an injured rib.

Lucas Matthysse overcame two early knockdowns and stopped John Molina Jr. early in the 11th round of the Argentine 140-pound star's dynamite return to the ring. Matthysse knocked down the bloody Molina in each of the final three rounds, culminating in a decisive combination.

Omar Figueroa Jr. also retained his WBC lightweight title with a split-decision victory over Jerry Belmontes on a chilly night before an energized crowd at the outdoor ring south of Los Angeles.

Thurman (23-0, 21 KOs), nicknamed "One-Time" for his knockout power, retained his WBA interim welterweight title by knocking down Diaz in the second round before delivering the body shot that apparently ended it. Although he had a short night, Thurman demonstrated his formidable skill and power in his seventh fight in less than two years.

"He's a warrior, but he just couldn't take the punishment," Thurman said of Diaz. "No one knows the power of One-Time until they step in the ring with One-Time. We did the work in the gym. How did you think I was able to look this good?"

Thurman was busy from the opening bell, and he dropped Diaz (40-10-1) in the second round with a left to the temple. Diaz stayed on his unsteady feet for a moment before taking a knee and getting up to beat the count.

Diaz took a barrage of body punches from Thurman in the third round, and his corner stopped the fight with Diaz on his stool.

The main event was an anticlimax after a tenacious performance by Matthysse (35-3, 33 KOs), who hadn't fought since injuring his eye and losing a decision to 140-pound champion Danny Garcia last September.

"It did take me a few rounds to get going, but I was able to take control of the fight," Matthysse said. "The knockdowns threw me off a little, but I was able to get my punches in."

That defeat interrupted the rapid rise of the hard-punching Argentine known as "The Machine," and he returned with what many expected to be a simple fight against Molina (27-4), a Los Angeles-area fighter who infamously got knocked out in the first round of a title shot in 2012.

But Molina showed he was no pushover from the opening round, knocking back Matthysse with a big right hand. Another chopping right out of a clinch in the second round sent Matthysse to his knees on just his second career knockdown.

Although Matthysse controlled long stretches of the bout with his jab and power, he went down again late in the fifth after winning much of the round, dropping to his knees on a punch to the top of his head. Matthysse immediately indicated the punch was illegal in the back of his head, but referee Pat Russell ruled it a knockdown.

Despite a cut near his left eye, Matthysse kept using his jab and power against Molina, who had a large cut on the left side of his head. Matthysse then knocked down Molina late in the eighth round with a left hand and a possible push before punishing him throughout the ninth.

Matthysse dropped Molina again in the 10th round with a combination on the ropes. Molina crumpled into the corner on a relentless barrage of punches early in the 11th, and Matthysse leaped on the ropes to celebrate.

Figueroa (23-0-1) gained a measure of revenge with a methodical win over Belmontes (19-4), who beat him several times when the two Texans were amateur fighters. Two judges favored Figueroa by 118-110 and 116-112, while a third gave it to Belmontes 115-113.

"That's just the way he fights," Figueroa said. "I wanted to put on a good show for the fans, but there's only so much I can do."