McLaren's Lewis Hamilton and Jenson Button say they are "excited" to start the new season, but have no idea whether they will be competitive.
McLaren hope to end Red Bull's dominant form from the last two years.
"I feel great. I'm very happy to be here. I'm excited for the new season - it's a fresh start," said Hamilton, who endured a difficult time last year.
"The team has been working hard to prepare us a car to fight with and I'm in fighting shape."
The feeling within Formula 1 is that Red Bull and McLaren will start the season in the best shape, ahead of a tight midfield battle headed by Mercedes and Lotus, who were named Renault last year.
But Hamilton said he was not heading into the weekend expecting to be in the fight for pole position with Red Bull drivers Sebastian Vettel and Mark Webber.
"I'm not expecting anything," he said. "I would like that to be the case, but whatever the car [we have] we're going to be working as hard as we can to get to the top and do the best with what we have.
"It would be silly to have any expectation and then say we are definitely going to be on the front row, because we might find out in the next couple of days we're not the quickest and we'd look silly.
"I'm not sure where we lie, but I think we're there or thereabouts."
Button echoed his team-mate's thoughts, saying: "We do all the hard work in winter testing, and then we all get very excited about coming here.
"I always enjoy driving around Albert Park and it's nice to come here after a good winter. I don't know where we are, but I'm excited about getting going."
Hamilton was in reflective mood after a winter spent recharging his batteries from a year in which he won three races, but also became involved in too many controversies on and off the track.
"I've just got to keep my head down and stay focused on one goal," he said.
"I still fee quite privileged to be here in F1. I'm 27 years old, it's my sixth year in F1, but I'm still one of the few people in the world who gets to do this job.
"I'm constantly having to pinch myself that I'm still able to be here. I'm very happy. I'm in a good place."
And he played down the importance of starting the season on a high - pointing out that he had finished second to Vettel in the season-opening race in Australia last year only for the German to go on to dominate the season.
"[A good start] is not as important as you probably think. It's about the consistency throughout the year."