Retired unbeaten boxing champion Floyd Mayweather has said, he is coming out of retirement to fight Irish Mixed Martial Arts, MMA star Conor McGregor. MMA's website said, the 40-year-old American wants to face 28-year old McGregor in June.Mayweather had matched Rocky Marciano's iconic 49-0 unbeaten career record, when he walked away from boxing as the welterweight champion in 2015.Speculation of a Mayweather-McGregor fight intensified in recent months, with the US star saying he is willing to meet McGregor in a boxing ring.