Silverstone: Lewis Hamilton recognised he had work to do after Ferrari`s Kimi Raikkonen and Sebastian Vettel lapped faster than the Formula One world champion in British Grand Prix practice on Friday.
"Ferrari look strong again here and they were right there with us today so it should be a good battle," the Mercedes driver said after finishing fourth in the day`s second session led by team mate Nico Rosberg.
Raikkonen was second and four-times champion Vettel, the only non-Mercedes driver to win this year, ended third.
"Hopefully we`ll find a bit more tomorrow otherwise we could find ourselves in trouble," added the Briton who leads Rosberg in the championship by 10 points going into his home race.
Hamilton won at Silverstone last year, on the way to taking his second title, and can count on the support of most of the expected 140,000 crowd on Sunday.
If they were disappointed not to see him dominant from the outset, they need only remember how he came back from the disappointment of misjudging the weather and qualifying sixth last year.
The champion, who has been on pole in seven of eight races this season, said it had been a good day generally.
"Not perfect, and we`ve got some work to do overnight, but the pace is decent," he said. "I didn`t have the ideal balance on the long runs and I`ve got a bit of work to do on setup. But otherwise it`s all been good.
"I`ve also gone back on clutch setup which feels really good so far, just like it did in the first few races."
Rosberg, winner of three of the last four races, had a difficult start to the day when he stopped on the track with a hydraulic issue that meant he missed much of the first session despite still ending up fastest.
"In the afternoon it went a bit better but there were also some little problems here and there and the car felt not quite perfect," said the German.
"It`s a very demanding track with lots of different types of corners and there`s still a lot work to do for us to find the right set up."