Charles Leclerc set the pace ahead of Sebastian Vettel to lead a Ferrari one-two in Saturday's final practice session for the Russian Formula One Grand Prix. Leclerc, who was also fastest in Friday's opening session before being deposed by Red Bull rival Max Verstappen, lapped the 5.8-km Sochi track in one minute, 32.733 seconds. He was the only driver to dip into the one minute 32s with Vettel, who benefitted from Ferrari's strategy to win last week in Singapore at Leclerc's expense, 0.316 seconds off the pace. Mercedes, who have never been beaten in Russia since the race joined the calendar in 2014, struggled with Lewis Hamilton and Valtteri Bottas third and fourth. Over a second off Leclerc's pace at one stage, Hamilton, who has won eight races this season and leads Bottas by 65 points in the overall standings with six races to go, wondered if the Brackley-based squad would be able to bridge that gap. "I don't know where we'll find that time," the Briton declared before improving to a time that was 0.396 seconds off Leclerc's best. Mercedes, 133 points clear of Ferrari in the overall standings, are well on their way to completing a record sixth title double with Hamilton. But they head into the championship's Russian round facing a fourth consecutive defeat, something that has never happened in Formula One's turbo-hybrid era, with Leclerc looking like the favourite to seal a fourth consecutive pole. Verstappen went fifth fastest for Red Bull. The Dutchman, carrying a five-place engine-related grid penalty, lost control of his car in the final stages of the hour-long session, easing backwards into the barriers. Romain Grosjean was sixth for Haas. British-born Thai rookie Alexander Albon seventh in the other Red Bull ahead of Renault's Nico Hulkenberg and Lando Norris, whose McLaren team had earlier on Saturday confirmed a return to Mercedes engines from 2021. Haas's Kevin Magnussen rounded out the top 10. Home hero Daniil Kvyat's nightmare weekend continued. The only Russian on the grid, the 25-year-old will miss Saturday's qualifying session after being sidelined by an engine problem in the final practice session. It will make little difference, however, with Kvyat set to start last anyway for Honda-powered Toro Rosso.