Mercedes set the pace in Portuguese Grand Prix practice on Friday with Valtteri Bottas quickest in the morning before seven-times world champion Lewis Hamilton led the way in the afternoon.
Red Bull's Max Verstappen, Hamilton's closest rival in the Formula One championship after two races, was second in both sessions at the Algarve circuit.
The start of the afternoon practice was delayed by 10 minutes as marshals fixed a loose drain cover.
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Bottas, his car rebuilt after a big collision with Williams driver George Russell at Imola on April 18, clocked a best time of one minute 19.648 seconds on soft tyres and was third in the second session.
Hamilton, only fifth in that opening hour, lapped in 1:19.837 in the afternoon.
"It's very windy today so I think everyone was struggling, sliding around out there," said Hamilton. "It's definitely been a real challenge today to keep the car on track.
We came here last year and the tyre was too hard and we've come here again this year with the same tyre, or even harder. It feels like we've come with too hard a compound in my opinion. I think it should have been mid-range."
The Briton leads Verstappen by a single point going into a weekend at a track where last October he won from pole and set the fastest lap.
"It looks like we're close," said Hamilton of the battle with Red Bull. "I don't know how Max's lap was, mine wasn't perfect so we've definitely got some time to come from the car... but I'm sure they have too."
Verstappen was 0.025 slower than Bottas and 0.143 behind Hamilton.
The Dutch youngster complained in the morning that the car was "impossible to drive" due to tyre vibrations.
"What a joke, mate. I can't even see where I'm going, there's so much vibration," he said over the radio. "I'll just visit the dentist after the weekend."
Red Bull's Sergio Perez was third and 0.198 off the pace after spending the early part of the opening session in the garage. He was 10th in the later stint.
Ferrari's Carlos Sainz was fourth in the second session with fellow-Spaniard Fernando Alonso fifth for a much improved Alpine.
George Russell, who collided with Bottas at Imola, was seventh fastest for Williams in another eye-catching morning performance by the youngster.
Four times world champion Sebastian Vettel, who has moved from Ferrari to Aston Martin, stopped at the wrong garage when he came into the pits during first practice.
"Sorry for that. It had to happen at some point," chuckled the German over the radio. "I was wondering why nobody was there."
Ferrari-backed Briton Callum Ilott took Antonio Giovinazzi's place at Alfa Romeo for his practice debut after being appointed as their second reserve earlier in the week. He was 17th fastest, with team mate Kimi Raikkonen 15th.
The Algarve circuit is hosting Formula One for the second time this weekend.
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