Mercedes is at risk of falling out of Formula 1's top three teams, Dr Helmut Marko has warned.

"(Fernando) Alonso will annoy Mercedes if they don't do something soon," said Red Bull's mercurial sporting boss after qualifying in Bahrain.

Indeed, Alonso's Aston Martin outpaced both George Russell and Lewis Hamilton on Saturday - a huge wake-up call for Mercedes' unique 'no sidepod' car concept.

"They (Aston Martin) gained two seconds in half a year and their car is half ours," said Mercedes team boss Toto Wolff. "Engine, gearbox, rear suspension. And the same wind tunnel.

"I don't think this package is going to be competitive eventually," he added. "We need to get our act together."

Mercedes was already toying with the idea of scrapping its current car concept, with Aston Martin's step forward now proving the precise problem area.

"It's the aero," Wolff said. "I think Aston Martin has shown how it's done. They did a total reset with their concept and found the right way."

Indeed, while the mechanical basis of Aston Martin's car is mainly Mercedes, the aerodynamic concept is much more Red Bull-like.

"If you compare the cars, you can see that the Aston Martin is most similar to Red Bull," Marko said.

"That certainly has its reasons. It wasn't just (Dan) Fallows who went to Aston Martin but also a few other people. And obviously they have a good memory."

Either way, racing away from the unique 'no sidepod' concept now appears to be imminent and obvious for Mercedes.

"Every day counts," said Wolff. "We are losing these days.

"We got it wrong last year, we thought we could fix it by sticking to this concept of car, and it didn't work out.

"Look at the pecking order - catching Red Bull is not realistic. We are relatively competitive against the Ferraris, not against Alonso, and certainly not against the Red Bulls."

Driver George Russell agrees: "We've probably got to a point where we do need to try something different."

In reality, however, the change of direction was almost certainly already in the works by the time the current car hit the track this weekend.

"It will not be a copy of other cars, nor will it look like what we have on the car at the moment," technical director Mike Elliott previewed. body check tags ::