It is testament to the quality of Valentino Rossi's riding this season that he comes to the latest round of MotoGP at Motegi in a very good position to secure his sixth world title, four races from its conclusion.

Victory at Indianapolis raises Rossi's advantage over Casey Stoner to 87 points and with only 100 points remaining this season, few would want to bet against the Italian from completing his endeavour in Japan.

So what exactly is required of Rossi this weekend? Perhaps the result he will be aiming for is a podium as third place will be enough for the title, regardless of what Stoner does. Failing that, should Stoner finish second, Rossi needs eighth or better, falling to 12th or 15th if the Ducati rider can manage no better than third or fourth.

The odds are certainly in Rossi's favour, not least because he has finished off the podium just twice in 14 races this season. Furthermore, Rossi has won six podiums at Motegi alone, while Stoner has had none.

Of course, it won't have escaped Stoner's notice that he could lose his crown at the very circuit he won it last season, but he will certainly be up against it this weekend. Admitting to struggling with his hand injury in the United States, the twists and turns of Motegi are unlikely to help much either.

If anything, he may spend the weekend keeping a watching brief on Dani Pedrosa, who comes to Honda's home circuit (they built it to host IndyCar races) desperate for a good result. Having made his Bridgestone-shod pneumatic-valve Honda debut at Indianapolis, the only way is up for the Spaniard and if HRC are going to pull out all the stops to win a race in a season, it will be here.

He too though is coming under increasing pressure in the overall standings from Jorge Lorenzo, who appears to have ridden out the storm of his injury-riddled mid-season, with a pair of good results at Misano and Indianapolis. Although he remains a fair 37 points adrift of countryman Pedrosa in the standings, should the Honda man continue to take time to adapt to his new machine, it could spur Lorenzo on to catch him.

Andrea Dovizioso was another rider to star at Indianapolis after leading early on and while he has lost ground to Lorenzo in the battle for fourth place overall, he still strengthened his position of fifth in the standings. With Honda rumoured to be confirming the Italian to their 2009 rider line-up this weekend, the bonus of having pressure off could help both him and the JiR Team Scot outfit to great things.

Beyond the top five, good performances are also expected from elsewhere in the field, not least from Loris Capirossi, winner at Motegi for the last three seasons.

The Italian has been unbeaten around the circuit since 2004, although this year he has the added challenge of winning aboard the Rizla Suzuki. A fourth straight win would mean more than just the continuation of a remarkable record though - it would also be his 100th podium and also make him just the second rider to pass the 3,000 career points mark in GP racing.

With a Ducati contract firmly in his pocket, Nicky Hayden is on a confidence high heading to Japan, a fact he displayed at Indianapolis with an impressive ride to second thus ending a 19 race podium drought.

That result has helped Hayden close in on sixth and seventh place riders in the standings, Chris Vermeulen and Colin Edwards, both of which will be looking for better in Motegi after a difficult outing in the United States. Edwards' Tech 3 Yamaha team-mate, James Toseland, meanwhile is also desperate for a good showing after a miserable weekend at Indianapolis.

With Yamaha, Honda, Kawasaki and Suzuki's presence making this round one of the most important of the season, there is certainly a Japanese influence on the grid. Most notably, Shinya Nakano will be keen to impress on home soil after a run of good results this season, while Suzuki will field a third bike for test rider Kousuke Akiyoshi too.

Elsewhere, buoyed by receiving a contract extension with LCR Honda for next year, Randy de Puniet arrives at the scene of his second place finish last season eyeing something similar, while Sylvain Guintoli, who finished fourth in Japan last year, will look to raise his stock as he looks increasingly likely for a World Superbike switch in 2009.

Finally, Kawasaki will be seeking a change in fortunes on home turf after their fine second place finish with de Puniet last season. Even so, having already finalised their rider line-up for next season, 'Team Green' have already admitted they are focusing on 2009 from now on.

The 250 cc riders arrive in Japan desperate for action after their race in Indianapolis was cancelled because of the weather. That was good news for Championship leader Marco Simoncelli who held onto his 26 point lead without lifting a finger.

The Italian Gilera rider will certainly be called into action on Sunday against Kallio's KTM team who have a superb Motegi record. Last year Kallio won the race to follow on to his two 125 cc victories for the Austrian factory while two years ago they were successful in the 250 cc class with local hero Hiroshi Aoyama.

Frenchman Mike di Meglio defends his 25 point lead in the 125 cc class and his nearest rival Italian Simone Corsi has got to start winning grands prix again if he's going to catch him. Corsi's last win of his three victories this season came at Mugello in early June.