The Repsol-Honda rider is all too familiar with the threat posed by prodigious rookie team-mate Dani Pedrosa, in second place in the title race trailing Hayden by 22 points after last week's Malaysian GP.

But now an even more formidable prospect haunts Hayden -- the need to halt a rampant Valentino Rossi and his devastating run of form at a circuit where the five-times 500cc champion has won the five previous Australian races.

The Camel Yamaha maverick rubber-stamped his late surge for the title with a nerve-jangling victory over fellow Italian Loris Capirossi at Sepang last weekend.

In the second leg of a crucial three-week series of races on Sunday, Rossi will be looking to close the gap on Hayden from its current 26 points ahead of the final three events of the season in Japan, Portugal and Spain.

"Phillip Island is a magic track for me. I've won a lot of races there and some championships too," Rossi said.

"After Laguna (where a blown engine left him out of the points in July) I didn't completely believe in my chances for the championship any more but then after Brno (where he finished second to Capirossi last month) I said to myself 'OK, we still have a chance'

"Now my objective is to win as many races as possible, then we see at (the last race in) Valencia."

REAL CONSISTENCY

Hayden, a model of consistency this season with 10 podium finishes, said he was still confident he could become the first U.S. champion since Kenny Roberts in 2000.

"I'm looking forward to having a strong weekend," Hayden said. "Every day and every session needs to be fast and consistent.

"I've got a strong team behind me so we'll give it all we've got for these final four races."

Spaniard Pedrosa, the reigning 250cc champion, is still bidding to shake off the leg injuries he picked up in a tumble during Friday practice at Sepang.

He finished third in Malaysia despite the handicap and was less than optimistic about his chances in Australia.

"I tested there during the winter so I have some experience of a MotoGP bike on the track, though it's not one of my favourite circuits.

"Let's see what the weather is like there - I think it will be cold."

Ducati's Capirossi and Fortuna Honda's Marco Melandri, who trail Hayden by 43 and 46 points, are the only other riders with mathematical chances of winning the title.

Hopes of a home success lie with rookie Casey Stoner, sixth in the world title race after finishing second to Pedrosa last season, and Chris Vermeulen.

"It's definitely a bit more important than most races, being my home Grand Prix," Stoner told reporters this week.

"I've still got to get results, I've still got to try and get podium wins and try and get myself out there a little bit more and try and get myself a better spot next year."