By Motorsport.com/GMMRed Bull is keeping cards up its sleeve ahead of the crucial qualifying session in Melbourne.
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
"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.