Floyd Mayweather will challenge WBC welterweight champion Carlos Baldomir in Las Vegas on 4 November.
Mayweather could fight Oscar de la Hoya next year
Mayweather, a former four-weight world champion, is unbeaten in 36 fights with 24 knockouts while Baldomir has won 43 and lost nine of his 58 contests.
Baldomir has not lost since 1998 and dethroned Zab Judah in January before stopping Arturo Gatti last month.
Both men have been touted as possible opponents for Manchester's WBA welterweight champion Ricky Hatton.
Mayweather, 29, took the IBF welterweight crown from Judah in April before giving it up and also stopped former two-weight world champion Gatti last year.
American legend Oscar de la Hoya says he wants to meet Mayweather before retiring next year.