IAAF president Sebastian Coe believes Usain Bolt is the most prominent sportsperson since Mohammad Ali and will leave a "massive void" in athletics upon his retirement.
Bolt is a six-time Olympic gold medallist and holds the world record in the 100 metres at 9.58 seconds and in the 200m with a time of 19.19secs.
The Jamaican will compete at Rio 2016 but is reportedly set to retire following the 2017 World Championships in London.
His impending retirement troubles the IAAF chief, who believes it will be a huge loss for the sport.
"He's going to leave a massive void, there's no doubt," Coe told The Telegraph.
"You'd look at me open-mouthed if I said anything different about the most widely-recognised sporting face on the planet.
"I can't think of anybody besides Mohammad Ali who has had such global visibility as Usain in the last 50 years."
However, Coe lamented the fact athletics enables Bolt to pick and choose which meets he participates in.
"It's like Barcelona announcing that Lionel Messi will not be playing more than 10 games a season," he added.