Mercedes driver Lewis Hamilton says that qualifying on the front row of the grid for the Singapore Grand Prix will be a tough task.
Hamilton was fastest in the first 90 minute practice session but slipped to fourth in second practice, over a second behind reigning world champion Sebastian Vettel.
"It wasn't the perfect Friday for us but we got on with our programme and know where we have to make improvements for tomorrow," said the 2008 world champion.
"The balance of the car felt really good in P1 but it definitely went away from us in P2. There is a lot of work to do this evening but we're used to that on a Friday night and will just get on with it and focus on our car and performance. It's so difficult to overtake around at this circuit that you want to qualify as high up as possible and, of course, aim for the front row but that will be tough."
"The circuit is much improved here without the chicane and Turn 10 feels like a much nicer corner now."
Team mate Nico Rosberg was third quickest and reckons tyre management will be key.
"We had a reasonable day but there is still some work to do this evening as our competitors seem to be very quick again," he said.
"We will be looking at how we used the tyres this evening and make sure we are on top of potential overheating and degradation on the long runs as there are no long straights here to cool the tyres down."