It’s doubtful that 2006 could have been much worse for Jose Luis Castillo.

First, he turned in perhaps the least-inspired performance of the year in February, outpointing safety-first Rolando Reyes over 12 dreary rounds.

Then, in the year’s biggest debacle, he failed to make the 135-pound lightweight limit for his rubber match with Diego Corrales.

It dealt a blow to a sport that is already chin-high in credibility concerns. And so Castillo retreated back to Mexico in shame, wondering whether boxing’s powers-that-be would be willing to take a chance on him again.

They did, and that chance arrives Saturday, when he meets undefeated Herman Ngoudjo at the Paris Hotel in Las Vegas.

For Castillo, 54-7-1 (47 knockouts), it’s an opportunity to right a wrong, while at the same time prove that he is still one of the best fighters in boxing.

It’s hard to believe that it’s been seven years — yes, seven years — since Castillo won his first world title, the WBC lightweight crown, from incumbent Stevie Johnston. At the time, no one was quite sure what to make of “El Temible,” other than that he bore a striking resemblance to his mentor, the all-time great Julio Cesar Chavez.

It was hard to make a determination about Castillo off of the Johnston fight. “Lil’ But Bad” was ridiculously tricky, and you wondered whether the challenger got lucky.

It wasn’t until his destruction of former champ Cesar Bazan in 2001 that he began to gain some notice. The left hooks to the body. The sneaky straight right hands. The constant forward movement. It was like watching a Chavez clone.

The impressive win over Bazan led to a defense against pound-for-pound entrant Floyd Mayweather in 2002. And, for most of the fight, Castillo did as he pleased against “Pretty Boy” Floyd.

He pressured him. He pounded the body. And he connected with solid punches — something foreign to most Mayweather opponents. Afterwards, it appeared

Castillo had done enough to retain his title. But, no. Mayweather got the nod and the title. Floyd got another decision six months later, and Castillo disappeared for two years.

Castillo reemerged in 2004, pounding out a 12-round decision over Juan Lazcano to win back his old title. After an early-2005 demolition of Julio Diaz, he was matched up with Corrales to unify the lightweight titles.

We all know what happened in that fight. The Castillo-Corrales original now resides in boxing lore as the best 135-pound title fight in history and, just maybe, the best pure brawl ever. That Castillo was on the losing end didn’t seem to matter much to either his fans or his career. In fact, the bruising affair enhanced his name and his marketability.

The fight was that good.

Castillo knocked Corrales out in the rematch five months later, under controversial circumstances. He failed to make the lightweight limit, for the first of two times. But Corrales agreed to fight anyway, without his belt on the line.

With a decided weight advantage, Temible made it look easy.

Castillo’s only fight since then was the waltz with Reyes, and he has consequently dropped off the radar.

Some magazines rank him in their pound-for-pound ratings, but who really knows? He’s 33 years old now, and campaigning in a new weight class, junior welterweight. Which means, he likely won’t hold his typical strength advantage. And his punching power may lose some voltage. That’s not a good combination when you’re a pressure fighter.

There’s also the element of the unknown in Ngoudjo, 15-0 (9 KOs), who hasn’t fought at the highest of levels, but had a nice win over Donald Camarena in his last fight, and defeated the tough Emmanuel Augustus in 2005.

Fighters who have never lost before always pose a unique, dangerous threat.

But, sometimes, a good, long rest is the most important component to the comeback of an aging fighter — as George Foreman proved in his unlikely, middle-aged return about 13 years ago. And as Oscar De La Hoya showed in May, looking like a million bucks against Ricardo Mayorga after a two-year sabbatical.

Maybe Castillo will follow suit.

If he wins, it’ll likely be on to a showdown with England’s Ricky Hatton, who is fighting Juan Urango for the IBF junior welterweight title in the main event. If it happens, Hatton-Castillo will be the ultimate youth vs. experience battle. And Castillo will likely be the underdog.

But, underdog or not, Castillo is just happy to get another chance. The Ngoudjo fight represents the road back, after a career lowlight. He’s just hoping he has enough left in the tank to take advantage of it.