Unbeaten American boxing star Floyd Mayweather says neither jail time nor ring rust from a one-year layoff will diminish him this week when he returns against compatriot Robert Guerrero.

"Of course I feel unbeatable. I'm in the sport where I'm the best," Mayweather said in a teleconference call last week. "I'm not going into the fight thinking I'm beatable."

Mayweather, 43-0 with 26 knockouts, will defend his World Boxing Council welterweight title against southpaw Guerrero, 31-1 with 18 knockouts, on Saturday at Las Vegas, a year after beating Miguel Cotto by unanimous decision.

Welterweight boxer Floyd Mayweather of the US works out at the Mayweather Boxing Club in Las Vegas, Nevada, On April 17, [Photo/Agencies]

It will be Mayweather's first fight since serving two months in jail for domestic battery, a fact that gives challenger Guerrero a confidence boost.

"Most definitely Floyd Mayweather is taking me seriously," Guerrero said. "It has been his longest training camp in a long time. Being a whole year's layoff, he's going to feel the punches. We're going after him the whole fight.

"It's going to take a little time to shake that ring rust off."

Mayweather, 36, says he is as fit as he has ever been and ready to face whatever challenge Guerrero brings.

"If that's his way to psyche himself up and build confidence, more power to him," Mayweather said. "I'm in tip-top condition. I'm in great shape. I have been working hard."

As for jail time, Mayweather would not say his stay behind bars changed him.

"It was just an obstacle that was in my way," he said. "I'm happy to be home. There's nothing cool about losing your freedom. Freedom is extremely important."

Mayweather, who will launch a six-fight deal over 30 months with the Guerrero matchup, has fought only four times since December 2007 and says resting his body for peak performance is far from losing fight fitness.

"I took a long time off before. I just call it a vacation," Mayweather said. "Sometimes the body needs time to heal. The body needs time to rejuvenate. The body needs time to rest."

Mayweather hinted at retirement after completing his latest fight deal, although a perfect run would leave him on the brink of a 50-fight win streak, and he said he would wait and see how he fared in the ring over the span.

"I only have 30 months left," Mayweather said. "After this fight I've got five more fights. That's all I have got to do, finish putting those stamps on my legacy. I just want to stay active, go out there and keep the fans happy. I don't know yet (if I will retire). I don't know. By 30 months, I'll be pretty close to 40. It might be time to get out of the sport. We have to see how these next six fights play out.

"I want to stay active. The busier I am, the better it is for me."

Mayweather termed Guerrero "flatfooted" and called him "more like a grappler, a wrestler, than a boxer".

"Everybody always says what they are going to do to me. He's a solid opponent. He talks a good game. Now we have to see if he can fight as well as he talks."

Mayweather said he was ready for any punishment Guerrero might bring, but ready to adjust his style to cope, saying, "You can't go to a gunfight and basically not think you're going to get shot. We have to see how the fight goes."

Mayweather will be trained by his father, Floyd Sr., rather than his uncle Roger because his uncle is ill. Mayweather has a strained relationship with his father.

"My thing is to try to leave all the negative things behind," Floyd Jr. said. "As far as arguments we had in the past, that's in the past. We leave it in the past and focus on the future."