Floyd Mayweather Jr has hailed the late Muhammad Ali as "a pioneer, a true legend and a hero by all means" following the iconic boxer's death at the age of 74.
The former world heavyweight champion - regarded by many as the best boxer in history - passed away on Friday, prompting a host of tributes.
Ali had battled Parkinson's disease for more than 30 years and was admitted to hospital earlier this week with a respiratory illness.
Mayweather, arguably the premier fighter of his era having completed 49 unbeaten fights prior to his retirement last year, was quick to acknowledge the impact of the man known as 'The Greatest'.
The 39-year-old posted a picture of Ali on Instagram, accompanied by the message: "Today my heart goes out to a pioneer, a true legend, and a hero by all means!"
Mayweather continued: "Not a day went by entering the gym that I didn't think of you. Your charisma, your charm and above all, your class are all of the elements that will be greatly missed by myself and the world.
"You are someone that inspired me greatly throughout my boxing journey and words cannot express how great you were as a person!
"Thank you for everything you've done for Black America, in the the world of sports & entertainment and for the legacy you leave behind!
"My sincerest condolences to the Ali family!"