` Nico Rosberg warns rivals Mercedes have not peaked yet . The German driver has been on a roll of late, winning the last three races and leading every lap in qualifying for his first race since suffering an engine failure at the start of this season. Rosberg leads drivers ' title race . Spanish Grand Prix takes place in Barcelona this weekend .
Nico Rosberg warns rivals Mercedes have not peaked yet . The German driver has been on a roll of late, winning the last three races and leading every lap in qualifying for his first race since suffering an engine failure at the start of this season. Rosberg leads drivers ' title race . Spanish Grand Prix takes place in Barcelona this weekend .