LONDON, Oct 12 - Valentino Rossi will be going flat out to prevent American Nicky Hayden dethroning him as MotoGP champion in Portugal on Sunday.

With two races to go, Honda's Hayden is 12 points clear of Rossi and can end the Italian's five-year reign as champion if he wins at Estoril and his Yamaha rival fails to finish higher than fifth.

It would be a surprise if that happens, however.

Hayden has not been in the top six in two previous visits to one of his least favourite circuits while Rossi has won four times and always been on the podium in six races at Estoril.

The 27-year-old Italian is on an amazing charge, having clawed back 39 points over the last four races after a nightmarish start to the season.

If he keeps it up, Rossi could be the one celebrating a sixth successive title in the top category of motorcycling when the season finishes in Valencia at the end of the month.

"Now we have two difficult tracks but I think our M1 can be fast at both of them," Rossi said in a team preview.

"Since Brno (the Czech Grand Prix in August), when we finally understood everything about what we needed to do to make our bike work at 100 percent again, we've been very strong everywhere and on the podium each time.

"I think that we're as strong as our rivals now and when we're at the maximum we're always going to be fighting at the front," added the Italian.

HUGE RACE

Hayden, 25, is the only MotoGP rider to have scored points at every race this year but he needs to be more than consistent on Sunday.

"It's a huge race for me," said the Kentucky rider. "I know that and I'm prepared for it.

"It's probably the track on the whole GP calendar that I've got the least experience at. I missed one year there because of my knee and collarbone and last year it was a wet race.

"Last year I didn't have a very good result there and I struggled a lot so I'm looking forward to definitely improve this time around."

Three other riders also have a mathematical, albeit slim, chance of the title -- Italians Marco Melandri and Loris Capirossi and Spaniard Dani Pedrosa.

Melandri is 27 points behind Hayden, with Capirossi a further four adrift and Pedrosa -- a championship contender until he fell and hurt his knee -- 34 off the pace.

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