SILVERTSONE, England -- Nico Rosberg provided further evidence of the threat he poses to championship-leading teammate Lewis Hamilton by posting the fastest times in both practice sessions at the British Grand Prix on Friday.
After Hamilton's storming start to his title defence, Rosberg has won three of the last four races to trim the Briton's lead to 10 points in the standings.
Not even a loss of hydraulic power early on Friday at Silverstone could prevent Rosberg topping the time sheets in a morning session that he was forced to spend mostly off the track.
"It was a difficult start to the weekend ... but incredible to see the crew get my car back on track before the end of the session," Rosberg said. "I was then able to attack for a few laps right at the end which was great."
The 30-year-old German completed the practice double during the 90 minutes on the track in the afternoon when he felt his car was "not quite perfect."
"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," he said.
Although Hamilton was only fourth fastest in the second session -- behind Ferrari duo Kimi Raikkonen and Sebastian Vettel -- the defending champion's lap in the morning was still the second fastest of the day.
During afternoon practice, Hamilton said over the team radio: "The car is all over the place. I can't go any faster."
"We've got some work to do overnight but the pace is decent," Hamilton said later in the paddock. "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. The tires feel strong. It doesn't take too long to warm them up which is a positive. I've also gone back on clutch setup which feels really good so far -- just like it did in the first few races."
That was when Hamilton opened the season by winning three out of four races -- with Vettel topping the podium in Malaysia to deny him a clean sweep.
"Ferrari look strong again here and they were right there with us today, so it should be a good battle," said Hamilton, who is chasing a third victory in his home race.
In his first season at Ferrari, four-time world champion Vettel sits third in the drivers' standings -- 39 points behind Rosberg.
"I'm not entirely happy with the car yet," the German said on Friday as he celebrated his 28th birthday. "Some of the things we tried were good and others were not so good."
