Based on winter testing, some believe the Austrian squad could be outpaced in Melbourne this weekend by Mercedes, Ferrari and Lotus, with McLaren also not far adrift.
Sauber, founder of the Swiss team that bears his name, agrees that Mercedes' pace at the end of the recent Barcelona test was "a clear exclamation mark", with Ferrari "not far away".
However, writing in Sonntagsblick newspaper, 69-year-old Sauber said he does not believe Red Bull is struggling.
"Anyone who concludes that they (Red Bull) are not right at the front are definitely in for a nasty surprise," he said.
"They have so many resources that they can always respond to difficult situations. You will see," added Sauber.