Max Verstappen conceded Red Bull have their work cut out even to qualify third at the Russian Grand Prix after Valtteri Bottas and Mercedes set the pace in Friday practice.
Bottas topped FP1 and FP2, beating Lewis Hamilton by 0.267 seconds in the second session when going head to head with the reigning world champion, who did not set a representative time in the opener.
Daniel Ricciardo - who has impressed for Renault with three consecutive top-six finishes – shone again by coming second and third, with Verstappen third in the first session before dropping to seventh in the next after a spin in one of his attempts at a flying lap.
Verstappen's team-mate Alex Albon was eighth and 12th across the two practices, so Red Bull are prepared for a tricky Saturday in Sochi, where the team have never recorded a podium finish.
"It will be tough in qualifying to be in P3," said Verstappen. "Clearly Renault are looking very competitive.
"I think in general we know that this track is not the best for us. We were trying out some downforce levels to see what is the best option.
"In FP2 I think we could have done better but we are testing a few things out - some worked, some didn't, so it gives us a few ideas for Saturday.
"It will be tough in qualifying but in the race it looks a bit more competitive so I am happy about that.
"First of all we have to look at ourselves and make the right trade-off with downforce levels as well, make sure the car is stable. Then I'd be quite confident that qualifying will be tight."
Albon added: "It feels tricky. We knew it was going to be hard, the midfield have obviously made a big step since last year, so it is a bit more tight.
"It doesn't feel bad, it's just everyone is very fast, so we need to do some homework and find out where we can gain those little bits."
The gap between Bottas and Ricciardo was over one second in FP2, with Mercedes looking primed for a seventh straight victory at the circuit – their dominant advantage coming despite both drivers making slight mistakes in their qualifying simulation laps.
A focused Bottas, who has not won since the first race of 2020, said: "There is still definitely more to come. There were quite tricky conditions and that's why we saw many people making mistakes."
Carlos Sainz – who recovered from an FP1 spin - and Lando Norris were fourth and fifth in FP2 for McLaren, with Sergio Perez sixth and both Ferraris making the top 10 to hint at an improved weekend for the Scuderia.