By Nick Mulvenney
MELBOURNE (Reuters) - World champion Sebastian Vettel is understandably favorite to open the Formula One season with a victory at the Australian Grand Prix this weekend but there are strong indications he will face a much tougher challenge than he did last year.
The German's pole-to-flag victory by a formidable 22.2 seconds at Albert Park last year started a second season of dominance for Vettel and his Red Bull team that culminated in the retention of drivers' and constructors' championships.
"This season looks like a stellar year for Formula One with six world champions. It's unprecedented," Red Bull team boss Christian Horner said. "The quality of the field is phenomenal. I think it's going to be a really exciting season.
"We're obviously determined to try and carry the momentum we've gathered over the last couple of years into this season, but we certainly don't take anything for granted."
Despite the millions of dollars invested in building the cars and the thousands of kilometers run in testing, no one really knows how the contenders will match up until the covers come off the tires for Saturday's qualifying session.
Indications are, however, that McLaren, who boast two of the former world champions in Britons Lewis Hamilton and Jenson Button, will be more competitive from the off than they were after a difficult winter last year.
"I actually feel more relaxed and ready for the new season than I think I've ever done," said Hamilton, who was fifth in the championship last year.
"Everything has gone smoothly with the car - which is more than we can say for last year - and it just seems to be a responsive and reliable package."
The 32-year-old Finn left the sport after battling with his motivation and, from what he showed in testing, would seem to have a car which could offer him the chance to fight for podiums at least.
"He looks like he is driving very well, like he has never really been away," said Horner. "So much will depend on the car for him, and that will probably affect his motivation."
Ferrari's former world champion Fernando Alonso, the 2006 winner in Australia, never needs any motivation but he and his team mate Felipe Massa look like facing an uphill battle to get on the podium in their radically overhauled 2012 car.
Seven-times world champion Michael Schumacher won the last of his four Australian Grands Prix in 2004 and his Mercedes team are another who have great hopes after positive winter tests.
"This will be my eleventh Australian GP and I can't wait to get started," said the 35-year-old, who finished third in the championship last year.
"It's been an extremely intense few months for the whole team and it's incredible when you count up how many sleep-deprived hours have gone in to preparing the car as best we can."
(Additional reporting by Alan Baldwin, Editing by Greg Stutchbury)