McLaren's Lewis Hamilton says his team-mate Jenson Button is his closest rival for victory in the Australian Grand Prix.
Hamilton led Button to a one-two in qualifying in Melbourne, 0.38 seconds ahead of Lotus's Romain Grosjean.
"Jenson's my biggest threat," Hamilton said. "I'm surprised to see the Red Bulls so far back and that we were so quick.
"I knew the car was good, but how good [compared] to others I had no idea."
Hamilton described the result as a "fantastic beginning to what I hope will be an incredible season".
World champions Red Bull, who have dominated the last two seasons, could manage only fifth and sixth places, with Mark Webber ahead of team-mate Sebastian Vettel, who has won the title for the last two years.
They are behind Michael Schumacher's Mercedes, which qualified fourth. Hamilton said: "I'm surprised to see [the] Red Bulls so far back and surprised to see that we were so quick."
Button added: "We expected to be fast, but we didn't expect to be six tenths quicker than the Red Bull.
"Six tenths is a big margin and I hope they [Red Bull] get used to it."
But Button said he expected the Red Bulls to challenge in the race on Sunday, which starts at 0600 GMT.
"We're going to have some competition over the race distance," he said. "The Red Bulls weren't that quick today but you can never discount them. I think they will be quick tomorrow, the same as Lotus and Mercedes.
"It's those four teams we have seen over the winter and this weekend that have been competitive.
"The gap between those teams, I don't know what it is yet. But I think it will be those four teams competing at the front."
He added: "To start the season with a win is massive for any driver. That's the aim. We're going to have a lot of fun tomorrow hopefully fighting for that."
McLaren had some nervous moments after qualifying when governing body the FIA spent three and a half hours checking their car to ensure it complied with the rules.
There was some concern about the height of the front wing, but it was eventually cleared.