Lewis Hamilton led the way for McLaren in the opening practice session for the Malaysian Grand Prix at Sepang as the Briton looks to put his difficult weekend in Australia firmly in the past.
With the main players sitting out the early stages of the session, Hamilton didn't hit the front until mid-way through and was followed on the times by team-mate Jenson Button.
The focus for most teams then turned to longer runs on heavier fuel loads, but Nico Rosberg put in a late lap that allowed him to split the McLaren duo and put his Mercedes into second place.
His team-mate Michael Schumacher followed Button in fourth place, although the German spent a lengthy part of the session in the pits as Mercedes worked on the rear of his car.
Robert Kubica was fifth fastest for Renault ahead of the Red Bull of Mark Webber, Force India's Adrian Sutil and points leader Fernando Alonso, while Sebastian Vettel was ninth having reported a possible issue with his car which was investigated by the Red Bull team. Sebastien Buemi rounded out the top ten for Toro Rosso.
Felipe Massa was eleventh for Ferrari having taken two trips across the gravel with Kamui Kobayasahi twelfth.
Paul di Resta made his second outing for Force India – replacing Tonio Liuzzi for the session – and was 15th quickest, while Fairuz Fauzy was 22nd for Lotus having been given the chance to drive on home soil.