Though red-hot favourites for another win, Mercedes admits to concern over tyre degradation.

In many ways those four bits of rubber have always proved to be the Brackley outfit's Achilles Heel, and even though the F1 W05 appears to be the class of the 2014 field - certainly at this early stage - the problem remains.

While Nico Rosberg and teammate Lewis Hamilton were quick to dismiss fuel consumption as a concern, both admitted that they are worried by tyre degradation, the British driver having claimed it felt like he was driving on marbles in the opening session, in which he posted the fastest time.

"It was a decent day, tough conditions, very, very hot and tough for the car, tough for the tyres even, we never expected so much tyre degradation," admitted Rosberg. "It's massive degradation out there which is a big challenge."

"It's the same every time I come here, it's to be expected," said Hamilton, who was giving precious little away. "Its too hot for the tyres, they are not working very well in these conditions. Even though we have got the hard tyre, the tyres do not feel great but that's the same for everyone."

"As was the case in Australia we've seen fewer marbles," said Pirelli's Paul Hembery, "but what was surprising was the amount of pick-up that we found on the circuit during FP1, with plenty of non-F1 rubber already laid down on the track.

"The surface cleaned considerably for FP2, which allowed us to have a more representative read of the track conditions," he added. "We've seen a performance gap of between 1.0 and 1.2 seconds between the hard and medium compounds, which should remain consistent if temperatures stay high. If temperatures drop slightly, we would expect the medium tyre to come more into its own. But we're still at an early point in the cycle of car development, so for everyone it's going to be a question of very carefully analysing the data that was obtained today when it comes to formulating a strategy."

"For sure there will be lots of different strategies and with the tyre anything can happen," said Rosberg. "It will always be close, we just need to try and stay ahead. Being on pole as important as it was, just getting that clean start away from the front is always a big advantage at the beginning of the race."

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Chris Balfe