Red Bull team principal Christian Horner fears his drivers will again be blown away this weekend when Mercedes crank up the power in Bahrain.

Although reigning four-times champion Sebastian Vettel finished a credible third in Malaysia on Sunday, behind a Mercedes one-two spearheaded by Lewis Hamilton, the 26-year-old German was a distant 25 seconds adrift.

Red Bull deserve an enormous amount of credit for being in a position where they are challenging for podiums given that in pre-season they suffered a catalogue of misery and appeared to be nowhere.

But on returning to Bahrain, the scene of two of the pre-season tests, Horner knows his team face a tough time at the Sakhir track.

"We can see we've got plenty to do to catch up with the Mercedes guys who have done a super job. They're in a strong position at the moment," said Horner.

"Although we've done incredibly well to get as close to them as we did in Malaysia, it's a big gap we face, and they've obviously got plenty up their sleeve.

"Their advantage is clearly in a straight line, but we're working hard with the guys from Viry (engine supplier Renault's base).

"Considering where we're at with the engine, to be doing what we are doing is beyond expectation.

"Renault know there is more to come once they sort out driveability issues and so on.

"In terms of catching up in straight-line speed, whilst our curve is steep, hopefully we should be able to make steps.

"But in Bahrain their advantage will be bigger than it was in Malaysia as that is quite a power-dominated circuit.

"We're not going to have a solution overnight - and it doesn't tend to rain too much in Bahrain either!

"We'll make as much progress as we can during the week, and hopefully we can nudge a bit closer to them again, if at all possible."

Red Bull fundamentally know they have a good car, but if they are going to make gains then that is down to Renault and correcting the software issues they have with the new power unit.

"We're a team, but it (the power unit) is a fundamental part for us to be able to compete," added Horner.

"A lot of their issues are software-related, so hopefully the steps can be made and we can close that gap.

"Hats off to Mercedes, they've done a very good job with this new engine and new technology, and we have to work very hard to catch them."