Agostini, who won 15 grand prix titles, eight of them in the 500cc, between 1966 and 1975, is to this day the most successful rider in the premier class.

In an interview to Italian newspaper Quotidiano Nazionale, the 77-year-old was asked of Rossi who has one fewer title in the main category.

Rossi has been in a slump of late, having retired in three consecutive races, and is in the middle of a winless streak that stretches back to the 2017 Assen race.

Agostini reckons that the 40-year-old Rossi is finally struggling to cope with his younger rivals, and has likened him to fellow sporting legends such as footballer Diego Maradona and boxer Muhammad Ali.

"Valentino does what he can, but he can't keep up and this creates problems for him," said Agostini.

"Vale is doing a lot, a lot, but the years pass. For everyone. They passed for Maradona, Cassius Clay [Muhammad Ali], [cycling legend] Eddy Merckx... They passed for me too, otherwise I would still be on the track today.

"The years are running and at a certain point you realize it and start thinking.

"We all want him to be there again, to always be number one, but I think it's clear to everyone that the opponents are much stronger.

"Valentino has fun and still wants to run. Valentino wants to be in that world and even if he gets fourth, fifth and doesn't win, he enjoys himself.

"He has the pleasure of running and this pushes him to face even difficult moments like this."

At the same time, Agostini is confident that Rossi can turn his form around at Yamaha, as the team will rely on his directions the most due to his experience.

"Valentino has been running and winning for a lifetime. He has a unique experience.

"Technically I think he knows more than any other rider, so if there's something wrong with Yamaha and there's something to change, his judgment and decisions will be the best. Always."