Sebastian Vettel and his Ferrari team enjoyed a strong showing in a curtailed second practice ahead of Sunday's Malaysian Grand Prix but it was a frustrating Friday for championship leader Lewis Hamilton.
Ferrari took the top two places after the afternoon session in Sepang as Vettel clocked a lap-record of one minute 31.261 seconds to top the time-sheets ahead of team-mate Kimi Raikkonen.
Both Mercedes drivers struggled and suffered spins in the session, Hamilton ending practice down in sixth, one place clear of the sister car of Valtteri Bottas and almost 1.5seconds down on Vettel.
The spins hurt the team's preparations for the weekend and their running was further truncated by a rain-affected first practice and a crash for Romain Grosjean in FP2 which saw the session red-flagged with over 20 minutes remaining.
No-one was able to improve on their times as Grosjean suffered a puncture when his Haas hit a drain on turn 13 which had seemingly had its cover ripped off moments earlier as Hamilton passed over.
Vettel is now 28 points behind Hamilton in the fight for the title after the Briton came here on the back of a hat-trick of wins, but the four-time world champion will take heart heading into what is set to be an inclement qualifying on Saturday.
Max Verstappen had gone quickest in the morning session, which was delayed by half an hour due to a heavy downpour, with Red Bull team-mate Daniel Ricciardo second.
The pair were third and fourth in the second session, albeit with Ricciardo quicker this time, while the McLaren of Fernando Alonso also went faster than the Mercedes as he went fifth.
The Force India duo of Sergio Perez and Esteban Ocon were eighth and 10th, with the Renault of Nico Hulkenberg sandwiched between.
Jolyon Palmer was next in the second Renault with Felipe Massa's Williams 12th and McLaren's Stoffel Vandoorne in 13th.
Lance Stroll was 14th ahead of the Toro Rosso pair of Pierre Gasly and Carlos Sainz, with Grosjean clocking the 17th fastest time for Haas before his incident brought the session to a premature conclusion.
The Frenchman suffered a massive puncture as his rear-right tyre bumped over the uncovered drain on turn 13 and saw him crash off into the wall at high-speed.
He was able to walk away from the car and confirmed he had not been seriously hurt.
Grosjean's Haas team-mate Kevin Magnussen was down in 18th with the Saubers of Pascal Wehrlein and Marcus Ericsson bringing up the rear.
The morning session saw no running in the opening half an hour as the track dried out following heavy rain.
Verstappen eventually led home Ricciardo with Vettel fifth and Hamilton sixth as Alonso enjoyed the rarity of a strong day by setting the third-fastest time during first practice.