Floyd Mayweather has announced plans for a September 14 fight with double light-middleweight champion Saul Alvarez.Unbeaten Alvarez outpointed Austin Trout in April to add the WBA belt to his WBC title, while Mayweather returned from a year out earlier this month to defeat welterweight Robert Guerrero.Between them Alvarez and Mayweather - the WBA’s Super champion at light-middleweight - are undefeated in 77 fights, and clamour for the two to meet has grown in recent weeks.Mayweather said: "I chose my opponent for September 14 and it’s ‘Canelo’ Alvarez. I’m giving the fans what they want. It will be at the MGM Grand.”At just 22 Mexican Alvarez, nicknamed ‘Canelo’ or ‘Cinnamon’ because of his distinctive red hair, represents a genuine physical test for an opponent 14 years his senior.The fight is due to take place on Mexican Independence Day weekend.