Fight of the year? How about fight of a lifetime.

Diego “Chico” Corrales (40-2, 33 KOs) and Jose Luis Castillo (52-7-1, 46 KOs) will be doing it again Saturday night when they fight for the WBO and WBC lightweight titles at the Thomas and Mack Center in Las Vegas (Showtime, pay-per-view).

It’s a rematch of the back-alley brawl they put on last May.

In that first fight, they took each other to the limit, and then ventured a little beyond it. It was the kind of fight that both shortens careers and defines fighters.

Corrales won that fight, but had to get up off the canvas twice in the tenth round to do it. After crawling to his feet that second time, he caught Castillo with a good shot and the war was suddenly on its way to being over.

“When (Corrales) went down twice, I thought the fight was won,” Castillo said through a translator in a recent conference call. “Maybe I was overconfident, but then I got hit and the referee stopped the fight.”

Asked how he felt when the fight was over, Castillo said he felt sad.

“Sad because I allowed myself to get caught when I had the fight won,” he said. “The fight got away from me. I just want my (WBC) title back.”

Right now, that belt belongs to Corrales, who realizes their second fight could demand as much of a gutsy performance as the first fight. But Corrales said he’s rested and recovered, ready to do it again if that’s what it takes.

“You just have to bite down and go,” he said. “You have to be prepared to go through the same thing again, every second, every round. I’m physically able and ready. If he’s not, that’s the edge for me.”

We’re guessing Castillo is also ready to bite down.

“It was a great fight and it ties us together forever,” Corrales said when asked if he thought about moving on past Castillo, maybe to something or someone easier. “It wouldn’t be right if I went on to something else.”

Joe Goossen, who trains Corrales, said there is no reason to expect the second fight to be any less brutal than the first.

“It was such a rough, brutal fight,” he said. “These are both aggressive guys. They never back up in a fight.”

Asked what he’s working on with Corrales, Goossen wasn’t about to tell secrets.

“I’d be remiss if I divulged any of my plans,” he said. “But I don’t think you’ll see much dancing around. It‘s going to be a very hard-fought fight . . . This is not a tea party. It’s a violent sport.”

Promoter Gary Shaw added a twist of his own.

“One of these fighters – Corrales – is a hunter,” he said. “The other – Castillo – is a rubber band. Every time you push him, he snaps back.”

That first fight had a little bit of everything, including controversy. Corrales eventually had a point deducted for spitting out his mouthpiece in the tenth. Castillo’s camp claimed he did it on purpose to get some extra down time. But Corrales blamed it on his dentist, saying he’d just had a couple teeth pulled.

“I’ve never been a dirty fighter,” he said. “I’m a straight-arrow fighter. That was the first time I ever lost a point in my life.”

Castillo wasn’t sold on the explanation.

“They might say it wasn’t intentional,” he said. “But it sure looked like it.”

For Corrales, maybe the best thing to come out of this fight was a little self discovery. He was forced to dig deeper then he’s ever had to dig before, and he was happy he still had something left when he got there.

“I always wanted my war,” he said. “You always wonder if you have it in you. And I did.”

Goossen knew he had it in him.

“The bottom line is, he’s willing to go to the end of the earth to get a victory,” Goossen said. “I love that about him.”