Malaysian GP: Rosberg and Hamilton say Ferrari 'looks great'

Despite the Mercedes drivers topping a session each at Sepang on Friday, the fact that Kimi Raikkonen ended up just three tenths adrift both times suggests that things could be closer than Australia.

Rosberg said: "It seems that again Ferrari is pretty close, so we need to keep an eye on them."

Hamilton was equally mindful of the gap to Ferrari, which traditionally runs less fuel on Fridays, but equally believed Mercedes had not shown its full potential yet.

"The Ferraris look great, they really do," he said. "It's surprising to see how good their times are. We will see if it continues this weekend.

"I know my lap wasn't spectacular. I think I have some improvements to make with the balance and settings, as they were all from the last race. I am sure we can improve it."

Hamilton's running on Friday was limited by a what the team described as "a failure on the power unit inlet system" and a precautionary stoppage when Mercedes lost telemetry.

He was able to get back out for the second session but admitted it was not ideal.

"Firstly it was an amazing job by my guys to rebuild the car, and get the engine and gearbox back on," Hamilton said. "I am grateful for that.

"Particularly here, where it is so hot and so difficult with the tyres out there, it was important to go out and get some laps.

"Fortunately I got a few laps with a longer run at the end. But in terms of set-up, we were not doing any changes, I've just driven what I have, and it is quite a bit off where I need it."