With just three rounds of the 2009 MotoGP World Championship to go, two of which are in the next ten days, Valentino Rossi knows he cannot afford any more 'off days'.

The Italian has seen his title lead over Fiat Yamaha team-mate Jorge Lorenzo cut from 30 to 18 points - after rear grip problems at Estoril were combined with a victory for Lorenzo, an impressive return to action by Ducati's Casey Stoner and a similarly fast pace by Honda's Dani Pedrosa.

Rossi knows that a repeat of that scenario this weekend at Phillip Island, a circuit notoriously hard on the left-hand side of the tyre, could put Lorenzo within striking distance of the title.

"Now we arrive at the most important moment of the season," said Rossi, speaking at Phillip Island on Thursday. "We have three races in a short time and this is the key moment for understanding who will become champion.

"In Portugal all three [Lorenzo, Stoner and Pedrosa] made a great race with a high pace, so it looks like Stoner and Pedrosa are in good shape to try and win this race. Especially Casey, who has won the last two races here and it is his home grand prix.

"That can be an advantage for me, or a disadvantage, like in Portugal," confirmed Rossi. "Now if we don't work at the maximum during practice and are not at 100 percent in the race, it is possible to finish fourth and lose a lot of points. So we have to concentrate and use all the practice to understand and improve the bike."

Just to add to the tension, the fast-changing Phillip Island weather is once again expected to play its part over the weekend.

"It is a great pity to come to Phillip Island at this part of the season because it is maybe the best track in the world, but at this time of year there is a good chance of rain," said the reigning six time MotoGP champion. "We don't have a lot of practice time anyway and the risk of rain is quite high all weekend, so we will have to use every second of practice to understand the bike."

Despite the weather, the picturesque Phillip Island circuit remains a firm favourite with Rossi, who was unbeaten at the Australian racetrack from 2001-2005.

"Firstly, Phillip Island is special because it is close to the ocean and it is unusual because it has a lot of left hand turns, much more than the other tracks in the championship," said the 30-year-old Italian. "The layout is fantastic because you are always at high speed.

"There are long corners where you are on the side at 200 km/h, plus some big ups and downs and blind braking. Also there is usually a big fight with slipstreaming in the race, so maybe overall it is the best track in the world."