Oz GP more open than ever, says Ralf

The German also said that his team is in good shape, although it will be some time before the full potential of the new FW25 chassis is realised.

"I don't think it has ever been so difficult to predict the outcome of a season's opening race," said Schumacher. "I think the consequences of the rule changes will have a more decisive effect that which team has the fastest car.

"I genuinely have no idea who will be ahead. All I know is that we have been working very hard on our car in order to make it as competitive as possible. We are in good shape, but it will take time until we have developed the full potential of the new chassis."

Schumacher's team-mate Juan Pablo Montoya has echoed the German's cautious optimism. He said: "We have been testing a lot during the winter and have arrived at what I believe is a good stage of preparation.

"I do think though that whatever each team has done over the winter, nothing really tells you where you are until the first GP weekend, and this season, the new rules will add some more uncertainty."

Williams has had a difficult winter, with the FW25 off the pace at several circuits. However, the team rebounded on the final day of pre-season testing on Friday, with Schumacher breaking the Jerez lap record.