Current MotoGP stars Valentino Rossi and Marc Marquez believe Australian Jack Miller’s jump into the premier class will be a tough task next season.

Seven-time world champion Valentino Rossi says Jack Miller is “very brave” to make the jump to MotoGP next season.

The experienced italian rider has warned the Australian to pace himself when he enters the premier class in 2015 with the LCR Honda Team and not expect results straight away.

Miller, 19, currently leads the Moto3 championship – the smallest of three cylinder classes in grand prix racing.

Rossi said the move from a 250cc KTM bike to 1000cc machinery will be challenging.

“The step is very big and Jack is very brave,” the 35-year-old said ahead of Sunday’s Aragon Grand Prix.

“I’ve spoken with him and he wants to do this.

“The bike will change a lot, the speed, brakes and tyres.

“He has to be clever and quiet and understand it all step by step and focus on getting results in the second half of the season.”

Reigning MotoGP world champion and current series leader Marc Marquez said it would be interesting to see Miller at Valencia in November for his first pre-season MotoGP test.

Marquez won the 125cc world championship in 2010, before going on to win the Moto2 title in 2012 and MotoGP crown as a rookie last year.

“When I was in 125cc I didn’t feel ready to go to MotoGP directly; I stayed in Moto2 because it was necessary for me,” the Spaniard said.

“For him, maybe it’s different. It will be hard at the start for sure, but we just have to wait and see.”

Miller agreed that it was a big step, especially given he only made the switch from dirt to road bikes in 2009.

“It’s a long-term project and with the time and attitude we can do it,” he said.

“It’s just a bike with two tyres and an engine.”

The Queenslander holds a narrow nine-point lead over Marquez’s younger brother Alex heading into Sunday’s race, the fifth last of the season.

“For sure, the championship is tightening up,” Miller added.

“Now we have to focus with five races to go.

“We had a test here previously at Aragon; I had a decent test and I think we can do a decent job here.”