Max Verstappen set the third fastest time on Friday in the first free practice for the Grand Prix of the Algarve.
Mercedes also dominated directly in Portugal.
Several drivers complained about a lack of grip on the Autódromo Internacional do Algarve, where a Formula 1 Grand Prix is being held for the first time.
Verstappen, Charles Leclerc, Sebastian Vettel, Carlos Sainz, Daniil Kvyat and Nicholas Latifi spun off the track without major consequences.
For a long time, Verstappen had the twentieth and slowest time to his name, because Red Bull was still looking for the right set-up on the Portuguese circuit.
With half an hour to go, the Limburger could improve considerably.
Mercedes soon found a good set-up.
Valtteri Bottas set the fastest time with 1.18.410, followed by teammate Lewis Hamilton at 0.33 seconds.
Verstappen admitted 0.78 second.
The Mercedes duo drove its fast times on the medium tire, while Verstappen had slower hard tires.
Ferrari driver Leclerc also drove on the hard tires and recorded the fourth fastest time.
Verstappen's teammate Alexander Albon was just within the second of Bottas in fifth fastest time.
All other drivers admitted more than a second.
Start times GP Algarve
Second training: Friday 4 p.m.
Third training: Saturday noon
Qualification: Saturday 3 p.m.
Race: Sunday 2.10 p.m.