Las Vegas, NV (Betting Express) - Jose Luis Castillo defeated WBO and WBC lightweight champion Diego Corrales by knockout in the fourth round of their non-championship, rematch bout at the Thomas & Mack Center Saturday night.

Despite the loss, Corrales will remain champion because Castillo came in overweight at Friday's weigh-ins, arriving two pounds over the 135-pound limit. He weighed in at 147 pounds before the fight on Saturday.

After Castillo landed a solid right hand towards the end of the third round, Corrales landed two right hooks on Castillo midway through the fourth. However, as Corrales went to throw a left, he opened up his right side and Castillo landed a devastating left hook that sent the American to the canvas.

Referee Joe Cortez began his count as Corrales crawled around on the mat. He reached nine as Corrales began to get to his feet, but the 28-year-old's legs gave out and he stumbled into the ropes. Cortez then ruled he had counted Corrales out, giving the knockout victory to Castillo with 47 seconds left in the round.

"I think, you know, his (Corrales') style is perfect for what I do," said the Mexican-born Castillo through an interpreter. "He comes in and he likes to be on the inside. That is what I love to do and it is just easier for me."

Despite the weight issue surrounding the fight, Corrales would not use that as a reason for his loss.

"I won't make no excuses, he just got me with a good shot," said Corrales. "I won't do anything to take from the credit of his win."

With the win, Castillo improved his record to 53-7-1 with 47 knockouts while Corrales fell to 40-3 with 33 knockouts.

Corrales won the WBC title from Castillo after a technical knockout over Castillo back on May 7.