Cam Newton reveals special birthday gift he received from Muhammad Ali

As the world continues to mourn the death of Muhammad Ali, Cam Newton has revealed a special moment he shared with the boxing legend.

In his Players' Tribune piece published on Saturday, the Carolina Panthers quarterback discussed the influence Ali had on his life and told how he once received the remarkable birthday gift of phone call from a man who transcended not only boxing, but sport as a whole.

"One of the most memorable moments in my life – one that I will always cherish – was when I received a surprise birthday call from Muhammad Ali," Newton wrote. "I could not have been more in shock and in awe.

"He finished the surprise birthday call in true Ali fashion. He said, 'You might be a good football player, but you will never be as pretty as me!'"

Since Ali's death was announced on Friday at the age of 74, tributes have poured in for a man whose influence spread across the world.

A funeral procession will be held in his hometown of Louisville, Kentucky on Friday.