Mercedes boss Toto Wolff says that Ferrari gain as much as eight tenths on the straights at the Sochi Autodrom as Charles Leclerc took his fourth pole position in a row since the summer break.
Mercedes were only able to qualify second and fifth with Lewis Hamilton and Valtteri Bottas, with Wolff putting it down to Ferrari's superior straight line speed.
Wolff told Sky Sports: "I'm really happy for the team. Lewis extracted everything from the lap - shame for Valtteri [going fifth] because he made the most of the lap as well. With seven to eight tenths lost on the straight [to Ferrari] there is not so much we can do. That's quite a massive amount.
"We have had many good season and many great races and now we have another challenge on our hands to fight."