Christian Horner is sure that the deficit from Red Bull to Mercedes is solely down to the new power units.

Nico Rosberg won the Australian Grand Prix by almost 25 seconds from Daniel Ricciardo on Sunday before Ricciardo was excluded from the results. That margin came even after a safety car period had bunched up the pack during the race, and Horner admitted that the signs were that Mercedes has a large pace advantage over his team.

"They controlled the race, I'm sure they didn't fully extend themselves and it looks like they have at least a second in the pocket at the moment," Horner said. "I would say on average it's about a second a lap, so that's about what we have to find."

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Asked if he felt that was mainly engine power, Horner replied: "Well based on the fact that we're giving away about a second a lap on the straights, I'll let you conclude..."

However, Horner feels that there is still plenty of progress that both the team and Renault can make, although believes the Malaysian Grand Prix will come too soon to challenge at.

"No [unlikely to win in Malaysia]. We've just got to use the two weeks that we've got between now and then to try and start to eke in to some of the gap that there is to the Mercedes.

"90% of the issues are software-related - how the energy recovery system is working with the combustion engine - so there is a lot of scope. We are tremendously restricted in the driveability of the car, how the torque is delivered, which obviously affects straight-line speed. So I think there is room for an awful lot of improvement, but it's working between the engineers in Milton Keynes and Viry-Chatillon to make sure we get the most out of it."