Alonso will skip the Monaco Grand Prix to contest IndyCar’s blue riband event, having set his sights on the Triple Crown of winning that race and the Le Mans 24 Hours to go with his two Monaco GP wins.

Rossi, who regularly takes part in rallying and has tested a variety of four-wheeled machinery including Ferrari F1 cars and a NASCAR on an oval in 2013, said he will be keeping an eye on how Alonso gets on in May.

“It was a surprise, because it’s strange that Alonso won’t race in Monaco,” said the Yamaha rider of the news. “But I think the situation with the car [in F1] is difficult and he wants to try something else.

“It will be very interesting to understand the potential of Alonso at Indy because it’s completely another world, especially when you race on the oval.

“The one time I went [on an oval] with NASCAR and it was very interesting, but you understand it’s very different.

“It will be a great challenge and very interesting to see.”

Marquez backs Alonso to shine

Honda rider Marc Marquez also admitted he was also surprised to learn Alonso would skip the Monaco race, but backed his countryman to impress on his debut in the US event.

“The decision is difficult to understand because Monaco one of the good tracks that maybe with McLaren he can get a good result,” Marquez said.

“[The Indy 500] is a race that’s difficult to understand from outside.

“You must be really lucky, slipstream is very strange, but the talent of Alonso, all of the drivers in Formula 1 say is one of the best ones in a car.

“His talent is there, I think he’ll be really fast.”