When Joan Guzman steps into the ring at Beau Rivage in Biloxi, Mississippi Saturday night to challenge lightweight champion Nate Campbell he has to worry about something the storm battered Gulf Coast has become accustomed to. He has to fear a power outage.

The undefeated two-time world champion is once again taking a dangerous step because he is not only walking up the three stairs that lead to the sporting version of Hades – the inside of a boxing ring – he’s also doing it at a weight unfamiliar to him.

It would be a difficult enough assignment simply to be facing the holder of the WBA, WBO and IBF 135-pound titles under the most optimum of circumstances but to be fighting for the first time at that weight after winning WBO titles at 122 and 130 pounds compounds what in recent years has become a growing difficulty for Guzman. So the question is when does a difficulty become a disaster?

For all his success, and he has had plenty, Guzman has of late struggled with what has become a notable power outage ever since first moving up from 122 pounds. Although undefeated and a two-time world champion at junior featherweight and junior lightweight, Guzman (28-0, 17 KO) has not knocked out an opponent in four years, six months and 16 days, a streak that now runs through seven fights dating back to Feb. 26, 2004.

Now he is moving up in weight for the fourth time, stepping into the 135-pound division ruled by Campbell and Manny Pacquiao, who won the WBC portion of the lightweight title several months ago by battering David Diaz into bloody submission.

Once Guzman was such a fistic force that he was nicknamed “Little Tyson,’’ a name that came to him because of his concussive punching power. He knocked out 17 of his first 21 opponents and was one of the most feared little men in boxing, but as often happens, as Guzman moved up in weight from 122 pounds to 126 pounds and finally to 130 pounds and began to face naturally stronger opponents his power did not come with him.

This did not preclude the talented Guzman from finding ways to win because he possesses a wide range of skills, good movement and command of any ring he is in. But he was no longer the same feared puncher he once had been, a point Campbell (39-5-1, 25 KO) has reminded him of at every turn.

“Guzman doesn’t know what’s going to happen to him,’’ Campbell said. “He has no idea where I’m taking him on Sept. 13. I love it when they feed me these guys with these big fat shiny 0s on their records. He’s a good fighter. He has speed. But he can’t hurt me.’’

There would seem to be more than circumstantial evidence to support Campbell’s conviction. Yet Guzman’s trainer, loquacious Floyd Mayweather, Sr., insists his fighter remains what he always was – a power-punching hurricane ready to strike the Gulf Coast with full force Saturday night.

“Joan Guzman is the man to meet if you want to go to sleep,’’ Mayweather said this week in Biloxi. “I like the match up. If everything is right, Guzman will win the fight. He’s no Juan Diaz, a one-dimensional fighter that just comes right at you. Guzman gives you a lot of different angles – slipping and sliding.

“No matter what, it should be a great fight. I look for my man to prevail – taking nothing away from Nate Campbell, who is an awesome fighter. I called Nate three weeks ago because I’d been hearing some things being said. I let him know that people are saying many things and I can only own up to what I have said. Nate and me are good.’’

If Guzman is just as good as he once was, or perhaps more importantly as heavy handed as he once was, this could be a fight with a concussive ending. If he’s not the same? Well, the same could be true.

The 36-year-old Campbell has implied as much, arguing that he will be making the first title defense of his long life in boxing against a man he insists cannot hurt him with an axe handle in his hands. If that is true, then Campbell seems sure to put the kind of suffocating pressure on him that broke down Juan Diaz when Campbell surprised the boxing world and wrestled the title from young Diaz in his last fight.

Yet if Campbell takes the same aggressive approach with Guzman as he did with the light hitting Diaz, the challenger believes the advantage will be his not Campbell’s.

“Most fighters think they have me figured out simply by watching my recent fights,’’ Guzman said. “Campbell is no different. He thinks he has the keys to victory but watching film and actually fighting me are two completely different things.

“If he thought I was fast and skilled on tape, wait until he tries to hit me inside the ring. It won’t happen. I’ll make Nate look so bad he’ll retire after I wipe the floor with him. Twenty eight boxers have tried to beat me and none of them came close to succeeding.’’

Some might debate that latter point but there’s no denying that no one has ever had his hand raised when in the ring with Joan Guzman. Then again, there’s also no disputing that this will be his first exposure to the kind of power carried by a natural lightweight as well as their ability to absorb punches from smaller men. It is a test Joan Guzman will not know if he can pass until late Saturday night after all the talking is over and the only thing left between him and a third world title will be a naturally bigger man named Nate Campbell.

It is then that the story will be written, although Guzman insists he already knows the ending.

“The weight won’t be an issue because I have a great strength and conditioning coach in my corner,’’ Guzman insists. “One of the goals in training camp was to adjust and maximize my speed and power to the lightweight division. Guys are bigger and stronger here so I needed to spice things up in the gym. I’m confident you’ll see the strongest, fastest and best conditioned Joan Guzman ever on Sept. 13.’’

Judging by the way he has looked in training that seems sure to be the case but whether you will also see anything near the Guzman once known as “Little Tyson’’ is another question. Certainly it has been a long time since anyone thought of even calling him that so why would this suddenly change by adding five pounds to his opponent’s frame?

Yet in his last outing Guzman dominated Humberto Soto while defending the WBO super featherweight title and he sees no reason he can’t do the same to Campbell or anyone else. Guzman beat him to the punch all night, using his speed advantage to land searing combinations while presenting an all but impenetrable defense for which Soto had no penetrating armaments.

Before that match Soto had talked just like Campbell, insisting Guzman couldn’t hurt him. If he didn’t hurt him physically he certainly hurt his feelings and his reputation, easily out boxing him to retain the WBO 130-pound title by wide margins on all three judges’ cards (117-111 on two and 118-110 on the third).

If he can do the same to Nate Campbell, Guzman’s punching power will become a non-issue. Of course, to do that he first will have to convince Campbell of that during what figures to be a bruising business meeting in Biloxi.

“Honestly, I believe I’m the total package,’’ Guzman said. “I’m not only one of the best punchers; I’m the best boxer at 130 and 135. Campbell is a very intelligent boxer as well as a fighter so it’s going to be a great fight but I know what I’m capable of. I can beat them all.’’

Joan Guzman may be right about that even if he can’t knock anyone out to make that point any more.