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.