Cal Crutchlow admits he doesn't understand the fluctuating form of Maverick Vinales, but has no doubts over the Spaniard's talent.

"I would say speed and talent wise, along with Marc Marquez, there is nobody faster in the championship. And he could win a world title with his eyes closed if he put everything together," Crutchlow said.

Qatar winner Vinales asked for the second season of his factory Yamaha contract to be annulled after hitting rock bottom with last place in Sachsenring, despite being back on form with second place a week later at Assen.

Crutchlow, who has worked with Vinales as part of his new duties as a Yamaha test rider, doesn’t understand the difficulties the Spaniard has been having this season, given the same bike has won four races and comfortably leads the world championship in the hands of new team-mate Fabio Quartararo.

And while the Englishman doesn't agree with the decision Vinales has made, he respects him for having the 'balls' to walk away.

"I can't understand it," said Crutchlow, back in the MotoGP paddock as a replacement for the injured Franco Morbidelli at Petronas Yamaha this weekend

"I'm a big fan of Maverick. He's a friend of mine. Even when I was racing, I had good relationships with most of the riders because I could separate it very well. In the track I wanted to beat them and they wanted to beat me, but we all had the same goal. So I understood what they go through in their life.

"But I really respect his decision in leaving Yamaha because that's what he wanted to do and it takes balls to do that, honestly speaking. I haven't seen anybody else do it except Zarco a few years ago and when I did it in Ducati.

"If he's not happy with the situation then he's done something about it. But I don’t agree with it, because I think that Yamaha absolutely over his whole time gave him everything that they could have every given him, without fail.

"The problem is, as we know, more what is going on with Maverick. But that's his feeling with the bike. It's not, I believe, a problem of the motorcycle or the manufacturer or the team.

"But if I look at Maverick Vinales, I would say speed and talent wise, along with Marc Marquez, there is nobody faster in the championship. And he could win a world title with his eyes closed if he put everything together."

Crutchlow added: "I like working with Maverick. Maverick is a character that's good for me because I'm older, I have a lot of experience and genuinely he's a good guy. I hope he has a good finish to the season because he, Yamaha and the team deserve it."

Vinales - who won a race for Suzuki in 2016, then won eight more with Yamaha since 2017 yet never managed a title challenge - is still to announce his new 2022 team, but Aprilia is the overwhelming favourite to secure his services.

"Having a top rider like Maverick for us would be the next step," said current Aprilia rider Aleix Espargaro. "I think for [Maverick] this project suits him very good. I know him well. He will be very happy if he can come here."

Mwanwhile, turning to the stunning success of Quartararo this season, Crutchlow echoed previous comments by Valentino Rossi that it’s the young Frenchman 'making the difference'.

"Fabio's making the difference. Because the others have what he has. So do I when I go testing. He's just riding fantastic, in a great way," Crutchlow said.

"He's great to work with as well. I like to work with Maverick because he listens and if you say something's better, he takes it. But I also like Fabio because he's stuck to his guns and he's doing well with what he's got.

"He feels comfortable with his setting. My setting on my bike is never going to work for Fabio, but my electronics or a linkage or swingarm that I find will. And some stuff has.

"But I like his stubbornness of 'this is what I ride, I don’t need to touch the bike' which he very rarely does and he just rides it. He's doing very, very well.

"But when you're 22 you're not so worried I don’t think about the setting of the bike. You're just worried about going fast and want to be at the top of the leaderboards.

"I remember feeling like that. I never was - but I can remember feeling like it!"

Quartararo holds a 34-point lead over Ducati's Johann Zarco heading into Sunday's Styrian MotoGP, round ten of the season.