Mercedes have triumphed at Sochi on each of the four occasions the Russian Grand Prix has taken place but team chief Toto Wolff says they cannot rest on their laurels as Lewis Hamilton closes in on a fifth Formula One title. Victory for the Briton last time out in Singapore, after a stunning pole lap which came out of nowhere, put him 40 points ahead of Ferrari's Sebastian Vettel with just six races remaining this season. Hamilton won in 2014 and 2015 in the Russian Black Sea resort when the race took place in October. It was moved to May and April in the last two years when teammates Nico Rosberg and Valtteri Bottas prevailed. Wolff is a little concerned by the switch in date.

"With the race being held in late September, we're going back to weather conditions that will be similar to those of 2014 and 2015, when the Russian Grand Prix took place in early October," he said in a team statement.

"We don't have any data from the current regulation cars in those conditions in Sochi, so this adds another challenge to the race.

"We have a good track record in Sochi but we know that Ferrari and Red Bull will give it everything to break our winning streak, so we must fight as hard as ever to make sure we bring home as many points as possible."

Vettel could only finish third in Singapore after questionable Ferrari tactics but has not given up hope of somehow overtaking Hamilton and snatching his own fifth world title having won four at Red Bull.

"I think Russia has improved in recent years for us, so it should suit our car," the German said. He has two second places in Sochi from 2015 and 2017.

"I don't think we have to worry about races that are yet to come. I think our car works pretty well everywhere. That's one of the strengths of our car, so there's no reason to be afraid of what's coming," Vettel added.

Counting against Vettel is the form Bottas has previously shown in Sochi. As well as having won in 2017, he made the podium in 2014 with Williams and was fourth in 2016. He would have been third in 2015 but for a Kimi Raikkonen calamity on the last lap. If the Finn produces another good showing, then the chances of more Hamilton success is increased given Bottas is a good team player and will try to help his fellow Mercedes driver in the title race. Red Bull duo Max Verstappen and Daniel Ricciardo look out of the running as they are expected to incur grid penalties for switching power units. The long straights at Sochi mean the track does not especially help Red Bull anyway.

"Sochi is going to be a tough weekend for us," said Red Bull team boss Christian Horner.

As for pit stops, a one-stop strategy looks the only way to go with no one has finished in the top four following multiple stops.