Gerhard Berger, who is famously close to Red Bull's inner circle, has admitted Mercedes is heading into the 2014 season as the favourite.
World champions Red Bull, powered by Renault, are in the midst of a technical crisis with the new RB10 car, while Mercedes has got off to a flying start in the revolutionary new V6 era.
"I am not surprised that Mercedes has built the best engine," former F1 driver and Austrian Berger, who last decade co-owned the Toro Rosso team with Red Bull, told Germany's Sport Bild.
He predicted 2014 would ultimately be a "struggle between the genius of Adrian Newey and Sebastian Vettel against Mercedes technology".
However, Berger sees a glimmer of hope for Red Bull.
"In 1989 at Ferrari we managed three laps in the pre-season but my teammate Nigel Mansell won the first race," he said.
But as far as Lewis Hamilton is concerned, Mercedes' pre-season is going smoothly.
"It's very difficult to know where we are in terms of performance," the Briton said in Bahrain on Wednesday, "but in terms of reliability we are in front."
When asked about Mercedes' apparent dominance in 2014 so far, however, Renault Sport's engineering chief Remi Taffin did not want to comment.
"It would be a waste of time to be looking at what they're doing (now)," he is quoted by Italiaracing.
"If we are in a position to beat them, then we will look at them," he added.