That is the view of Mercedes' Norbert Haug, who warned that the practice timesheets so far should be read with caution.
"If Sebastian Vettel wanted, he could be a second faster," the German is quoted by O Estado de S.Paulo newspaper, before Vettel upped his pace to be a second quicker than the nearest non-Red Bull in Saturday practice, Lewis Hamilton.
"So, no matter how much progress we have made, Red Bull is still way ahead," added Haug.
Michael Schumacher agrees: "I'm sure they have not showed their full potential."
I'm sure they have not showed their full potential
McLaren's Jenson Button was quickest late on Friday but he is also wary of Red Bull.
"I know they weren't using their (adjustable) rear wing when they set their quick laps, so they have another five or six tenths available to them," he said.
Fernando Alonso, however, said before travelling to Australia that he thought McLaren would be in the running this weekend.
"There were those who said Ferrari and Red Bull are ahead of everyone, so whoever is surprised now about McLaren is their problem, not ours," he is quoted by the Spanish newspaper Sport.
McLaren team boss Martin Whitmarsh told the BBC on Saturday: "I don't think we have seen the best from Red Bull but I hope we will be giving them a hard time."