Nico Rosberg timed the fastest in the first free practice at the China Grand Prix in Shanghai on Friday.
Rosberg clocked a fastest lap of one minute, 38.037 seconds after a late dash with world champion Lewis Hamilton second quickest, just 0.146 behind, in the other Mercedes.
Ferrari's Sebastian Vettel was third. Ferrari has been the most successful team in China with four victories -- including the last of Michael Schumacher's record 91 race wins 10 years ago.
Red Bull's Daniel Ricciardo posted the fourth fastest lap with Kimi Raikkonen fifth in the second Ferrari after a late surge.
Meanwhile, Fernando Alonso returned for McLaren after his horror crash at the season opener, the Spaniard setting the 12th fastest time.