Having recently turned 40, Valentino Rossi now finds himself racing against a rider less than half his age.

Rookie Fabio Quartararo will be just 19 years and 324 days old when he lines-up on the grid with fellow Yamaha rider Rossi for the opening round of the new MotoGP season, in Qatar, on Sunday evening.

The pair were seated next to each other during Thursday's pre-event press conference at Losail, when Rossi admitted they had already spoken about the age difference.

"We speak now exactly about this, I said that he could be my son!" smiled Rossi. "He's very, very young. [Born in] 1999, so it means that he's also two years younger than my brother [Luca Marini] and already in MotoGP."

Quartararo arrived in grand prix at just 15-years-old, having won nine of eleven races in the CEV Moto3 championship for Emilio Alzamora's team.

It prompted comparisons with Alzamora's earlier protégée Marc Marquez, but after two podiums in his rookie grand prix year Quartararo split with Alzamora and didn't win a world championship race until last season in Moto2.

That victory helped secure a surprise move to MotoGP with the new Petronas Yamaha team, with which the Frenchman was a shock second quickest at the final pre-season test.

"[Quartararo's] had a strange career," Rossi said. "He arrived like a genius but after for some reason he lost a little bit the way. But I think that this year, with this team and this bike, he has a very important chance to demonstrate his speed. It will be interesting - and I'm very sorry that he can be my son!

"He's also arrived one year earlier than me in MotoGP, because I was already 21."

Quartararo will become the third rider to start a full-time MotoGP season as a teenager, after Michel Fabrizio and John Hopkins, since the introduction of the four-stroke class in 2002.