Valtteri Bottas remained coy following Mercedes’ impressive display during Formula 1 practice for the Russian Grand Prix, believing the rival Ferrari team is yet to show its true pace in Sochi.

Mercedes swept to a one-two finish during second practice at the Sochi Autodrom on Friday afternoon, with championship leader Lewis Hamilton leading home Bottas, as well as finishing more than half a second clear of Ferrari’s Sebastian Vettel.

Vettel said after the session that Ferrari had “some catching up to do,” but while Bottas was pleased with Mercedes’ showing, he refused to read too much into its pace compared to its primary rival.

"It was a good day for us. On paper it looks like we should be competitive, but it's only Friday,” Bottas said.

“The initial feeling of the car was good. However, there's still work to do. It's so difficult to get a perfect set-up for each corner on this track, because the balance is so different throughout the lap.

“We brought some aerodynamic updates to the car that worked well and added more grip; we'll see if that's going to be enough for the weekend.

“It seemed like Ferrari weren't really showing everything they have, so they will probably be stronger tomorrow. I think it's going to be very close, so we'll have to keep pushing.”

Pace-setter Hamilton felt he had been able to put into practice some of the lessons he had learned after failing to win either of the past two runnings of the race in Sochi.

“Sochi has been one of the weaker circuits for me in the past, particularly last year,” Hamilton said.

“I’ve done a lot of work to understand the balance and see where I can improve to try and rectify this - today has been good in that sense.

“From every race we're learning more and more and particularly the last few races have helped us to really gauge which foot we need to start on for the weekend.

“We've brought more upgrades this weekend; there's so much work going on at home and it's just really encouraging when you come to a race and you get an upgrade, knowing that this late in the season we're also already working on next year's car - it motivates me to get the best out of everything.

“It's been a good day for us, so let's hope that it continues tomorrow.”