MOTEGI, Japan - Australia's Casey Stoner, fresh from winning the season-opening race, knows reigning world champion Valentino Rossi will be hot on his heels at the Japanese Grand Prix on Sunday.

"At this stage Valentino has been the hardest rival in testing and we know that Valentino will always be there," said the Ducati ace, who edged his Yamaha arch-rival by eight seconds at the Qatar Grand Prix two weeks ago.

"But people should always expect the unexpected. You don't know what other riders are capable of," added the 23-year-old.

But, with the Japanese GP pushed forward to be the second of 17 rounds this year, the rivals admit they have their work cut out in setting up their bikes.

"We haven't tested here in pre-season whereas we had in Qatar. So we'll see how we get on starting from zero," Stoner said.

Rossi said he would go out "with a positive image in mind" at Motegi where he beat Stoner into second spot and wrapped up his sixth premier-class title last September with three races to go.

"My memories of last year at Motegi are incredible because it was such a special victory after two years without the championship," said the jovial 30-year-old Italian.

"This year of course will be very different. It's only the second race and it will be quite strange going there so early in the championship.

"In Qatar we had one or two small areas that could have been better. So we will be trying hard to improve our setting during the practice time so that we're able to run at the front on Sunday," he added.

"I expect that Stoner will be strong again, so we just need to reduce the gap to him so that we can put up more of a fight."

Stoner's second place last year was his only podium so far at Motegi, which has only a few fast corners and many slow ones linked together by medium-long straights that put the acceleration of the bikes to the test.

"I have always thought that the track is more suited to car racing than bikes, with so many hard braking and acceleration points," Stoner said.

"But in general I don't dislike it and if you have a good set-up it can be really fun."

Rossi broke his jinx at the Honda-owned track last year after winning once but finishing runner-up five times. He crashed in 2005 and finished 13th with a mechanical problem in 2007 when Stoner secured the championship.

"In the past Motegi hasn't been a great track for me and I've had some bad races here," admitted Rossi. "But I think last year cancelled that all out so I hope it can be successful for us once again this year."

Honda is pinning its hopes on Spain's Dani Pedrosa, who finished third here and third overall last year, although he is still injured from a pre-season crash. He was 11th in Qatar.

Rossi's Yamaha teammate and another Spaniard, Jorge Lorenzo, will carry the momentum of his third place finish in Qatar.

Italian Suzuki rider Loris Capirossi, unbeatable at Motegi from 2005 to 2007, is looking to bounce back from Qatar where he crashed out.

The Motegi race is the 700th Moto GP race since 1949.