Ferrari’s Sebastian Vettel dominated second practice for the Malaysian Grand Prix, as Mercedes struggled, with the session shortened after a dramatic accident for Haas’ Romain Grosjean.
Vettel was quickest during runs on the Soft and Supersoft compounds in the dry session, with his best time, a 1:31.261, proving to be 0.604s faster than Ferrari team-mate Kimi Räikkönen.
Mercedes had a lacklustre session, with both Lewis Hamilton and Valtteri Bottas having off-track moments during the Soft runs early in proceedings.
Hamilton spun at Turn 7 while Bottas drifted wide on the entry to Turn 10; both had to negotiate their way through the gravel before slowly recovering to the pit lane.
Hamilton and Bottas also lagged behind their rivals during one-lap runs on both the yellow- and red-banded compound.
Hamilton finished the session in sixth position, with Bottas seventh, the pair over 1.5 seconds down on title rival Vettel.
The session came to an end after 70 of the scheduled 90 minutes in the wake of a high-speed incident for Grosjean, who was pitched into the Turn 13 barriers after a loose drain cover ripped his right-rear tyre to shreds.
The drain cover on exit the downhill right-hander of Turn 12 had been loosened moments beforehand by Bottas, and a helpless Grosjean struck the lifted cover.
Grosjean’s right-rear tyre was immediately ripped from the rim in the impact and the Haas driver was sent across the Turn 13 gravel trap, before suffering an impact with the barriers. Grosjean was able to walk away from the scene uninjured.
Following the incident, which occurred with 20 minutes of the session remaining, Race Director Charlie Whiting and Deputy Laurent Mekies inspected the affected area.
It was announced shortly afterwards that the session would not be restarted.
"I didn't see anything and then suddenly I had a big hit on the right rear," said Grosjean. "I'm good and fine, that's the main thing."
Red Bull emerged as Ferrari’s primary rival, with Daniel Ricciardo third and Max Verstappen, who topped the wet first session, in fourth.
Ricciardo wound up 0.838s behind Vettel, while Verstappen finished just 0.010s down on his team-mate, having completed an additional low-fuel run on Supersofts compared to his rivals.
Mercedes’ lack of pace was such that McLaren-Honda’s Fernando Alonso put his MCL32 into fifth spot, edging a tenth of a second clear of Hamilton.
Force India’s Sergio Pérez took eighth position, as team-mates past and present Nico Hülkenberg and Esteban Ocon rounded out the top 10.
Jolyon Palmer finished 11th for Renault, while McLaren’s Stoffel Vandoorne split Williams pair Felipe Massa and Lance Stroll, the Canadian youngster clipping the pit entry bollard after locking up into the hairpin.
Toro Rosso debutant Pierre Gasly edged team-mate Carlos Sainz Jr. for 15th, while Grosjean set only the 17th best time, before his dramatic exit, in front of Kevin Magnussen, the Dane complaining of "crazy" understeer.
Sauber again struggled in dry conditions, with Pascal Wehrlein nine-tenths behind nearest rival Magnussen, leaving Marcus Ericsson, via an off-track moment at Turn 9, half a second adrift at the back.