Sebastian Vettel says he is wary of the challenge from Lotus and Ferrari ahead of this weekend's Bahrain Grand Prix.
Vettel was third fastest in second practice, a tenth of a second behind Fernando Alonso.
"It’s pretty close. If you look at the opposition then Ferrari and Lotus were strong today and I think it will be close in qualifying," said Vettel.
"It’s important to work with the tyres around the track. I wasn’t so happy with my short runs today – but that’s why we have the Friday practice sessions I guess; I was happier with the longer runs. The tyres still seem to be the dominating factor. The car seems quick, so we have to make sure we use that and then we should be on the right page."
"We still have areas to improve on the car. Lotus and Ferrari look strong and Mercedes is there too," added team-mate Mark Webber, who was second fastest.
Webber, who takes a three place penalty into qualifying, reckons that while determining grid position is not as important as it used to be, it is still vital to preserve tyres on Saturday.
"Saturdays are perhaps becoming less important overall than they used to be, but they’re still important in terms of traffic. You don’t want to be in too much traffic on Sunday, as the tyres don’t like being disturbed and wear more which will shorten your first stint," he said.