Jose Luis Castillo's knockout victory over Diego Corrales has to taste a little bittersweet.

After losing the undisputed lightweight title in dramatic fashion to Corrales in May, Castillo KO'd the new champion in front of many of his loyal fans at the Thomas & Mack Center in Las Vegas last night, exacting revenge but not extracting the Ring Magazine belt from Corrales' waist. That's because Castillo, although winning the rematch, lost the battle on the scales when he failed to make weight, thereby rendering the fight a non-title bout.

At the pre-fight weigh-in, Castillo weighed 137 pounds in his first attempt. Two hours later he weighed 138.5 pounds. After a third attempt he weighed the same; Corrales made 135 in his first try. Castillo was therfore fined ten percent of his purse (which went to Corrales) and the fight lost some of its lustre when it was changed to a non-title bout. Promoters for Castillo and Corrales, Bob Arum and Gary Shaw exchanged heated words over concessions dealing with Castillo's night-of-the-fight weight and allegations arose of Castillo having personal problems during training, causing a spectacle that was in stark contrast to the first fight, in which the talk leading up to it consisted of how the fighters were in peak shape and were coming off career-defining wins.

Nevertheless, the excitement in the air was still palpable as the fighters made their ring entrances, but this one was not the classic many had hoped for.

The first two rounds had both fighters exchanging at close range, as they did for much of their first encounter. In the next round, Castillo landed a right hand that got Corrales' attention. In the fourth, Castillo landed a monstrous left hook, flooring Corrales and ending the fight six rounds short of their four-month old classic.

Castillo, 53-7-1 (47), who revealed he was fighting with a rib injury suffered during training, apologized for not being able to make weight and said it would never happen again. In allowing himself to balloon up in weight, he had a percentage of his first million dollar payday deducted and wasted an oppurtunity to retain his title. Corrales, 40-3 (33), realizing that it was safe to praise Castillo since he had nothing to lose, gave the Mexican full credit for his win and said he had no excuses. To Corrales' tremendous credit, he said he would invoke the rematch clause. He could easily walk away with his titles intact, but "Chico" is a warrior, who, like Castillo, knows that pride and dignity are essential to being a champion.

And so, if Corrales stays true to his word, look for Castillo-Corrales III, probably sometime late next year.