Thiago Alves Thiago Alves

Thiago "Pitbull" Alves withdrew from a UFC match Saturday because CAT scans revealed a brain irregularity, but he is aiming for a quick return to the sport, his agent said.

The 26-year-old, one of the top welterweights in mixed martial arts, failed several pre-match CAT scans and will now see a specialist for further evaluation.

"Hopefully everything's OK. We think it is," Alves' agent, Malki Kawa, told "As soon as a doctor says that it is, he'll be cleared and back to fight. UFC has promised that he will fight right away."

The tests showed "absolutely no bleeding or swelling" in the brain, but doctors located a problem with an artery and decided to err on the side of caution, Kawa said.

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Alves, who had been nursing a knee injury, has not fought since losing the UFC welterweight title to George St-Pierre in July. Saturday's highly anticipated showdown with Jon Fitch was supposed to be a rematch of their 2006 Ultimate Fight Night battle, which Fitch won."We're disappointed. Thiago's disappointed. He was really looking forward to this fight," Kawa said. "He really wants to fight him bad. It's just unfortunate, but his health comes first."Alves still plans on attending his previously announced meet-and-greet at a New York City restaurant on Friday, where he hopes to have new information to share, Kawa said.Due to the late withdrawal, Alves will not be replaced in the Saturday bout; instead, Kurt Pellegrino and Fabricio Camoes will be the night's main fight, UFC said.