Vettel, who is aiming for his fifth-straight drivers' championship, was brought down to earth at a rainy Albert Park street circuit, finishing well off the pace of pole sitter Lewis Hamilton and his new Red Bull teammate Daniel Ricciardo.
The German described the handling of his car as "horrible" during pre-qualifying practice, and things only got worse in qualifying
"Once it started to rain, I was struggling with drivability ... it made life pretty difficult," Vettel said.
Though disappointed with his own poor grid position, Vettel was buoyed by Ricciardo's performance, which indicated Red Bull was not far off the pace of the front-running Mercedes despite a trouble-strewn preseason in which the team suffered an array of problems with the new V6 turbo hybrid engine.
"There is performance in the car and that is the important thing," Vettel said. "We have a quick car and we just need to make it robust and reliable, but that's better than having a robust and reliable car and trying to make that quick."
Vettel was at a loss to explain why Ricciardo's car was apparently so much easier to drive.
"There was not supposed to be a difference between the cars so today was not too happy on my side and we need to understand that, but fortunately it worked for him, so at least we have one car where it belongs."