Defending Formula One champion Sebastian Vettel is entering uncharted territory. Not only is F1's youngest champion heading into the season as a marked man, the Red Bull driver goes into Sunday's Australian Grand Prix coming off preseason testing that left questions about those seeking to dethrone him. "How good we are in the end compared to the others has a bigger question mark this season than any other season before," said the German, 23. "In previous years you had an idea of where you were and where the others were at the end of the test season, but this year it is almost impossible."
Even so, it seems likely that Vettel's challengers will come from the same drivers who pushed last year's title fight to the final race.
McLaren drivers Jenson Button and Lewis Hamilton have credentials as former champions but might not have the cars, and Michael Schumacher, 42, is an outside bet to add to his seven titles with Mercedes.
Red Bull and Ferrari, both strongest in the test sessions, should dominate again — meaning former champion Fernando Alonso and Red Bull driver Mark Webber are shaping up as the main threats.
Drivers normally have one race behind them before the Australian Grand Prix, but the cancellation of the Bahrain GP kept the suspense going a little longer, heightened by erratic testing performances.
Vettel became the youngest F1 champion last year, finishing third in the final race to edge Alonso by four points.
Vettel faces a different pressure now, having taken the overall lead only in the final race last year.
"It will be a tough, tough battle and a long, hard fight," he said. "Motivation is not a problem. It's a more difficult situation than last year."
Vettel knows Alonso is desperate to make up for that final-day loss, when clumsy orders in Abu Dhabi derailed the Spaniard's bid for a third title. At 34, Webber's chances of a first title are running out. But both are strong contenders because of the reliability shown by Red Bull's RB7 and Ferrari's 150th Italia in testing.
It could be a frustrating season for 2009 champion Button and 2008 winner Hamilton if McLaren's patchy form in testing is not ironed out.
Hamilton said they could be struggling in the early races.
"Do I believe I have a car to win the world championship at the moment? I don't," Hamilton said recently. "But that doesn't mean it won't become a world championship-winning car."
Meanwhile, among several changes from FIA, the sport's governing body, the switch from Bridgestone to Pirelli tires is the most glaring.
The softer Pirellis have been designed to degrade more quickly in the hopes of creating more pit stops and lead changes as teams take risks over pit strategy.
And FIA banned aerodynamic boosts such as last season's innovative F-duct and 2009's double-diffuser, while returning the hybrid KERS (kinetic energy recovery system).
The adjustable rear wing is set by the push of a button from inside the cockpit, which lowers a flap and increases straight-line speed.
"We will definitely stop more often," Vettel said. "Probably every five to 20 laps, so this will have a huge impact on how the race unfolds."
Practice time: Button posted the fastest lap of 1 minute, 28.854 seconds in the second practice session Friday, 0.132 seconds ahead of Hamilton.