Ferrari can take the fight to Hamilton in Sochi qualifying
Vettel impresses in Friday practice
Channel 4 & Sky Sports F1, 1pm Saturday
Mercedes have dominated at the Sochi Autodrom since the first Russian Grand Prix in 2014, but they could have a fight on their hands this year.
The Silver Arrows have started from pole position in all three Russian Grands Prix and led every lap raced there. However, Lewis Hamilton and Valtteri Bottas could have a tough job keeping that record intact judging from practice evidence.
Sebastian Vettel headed a 1-2 for Ferrari in Friday afternoon's practice session after teammate Kimi Raikkonen had set the pace in the morning.
Notably, Vettel's pace on the longer runs later in the day suggested Ferrari are in very good shape for the race as well.
The fastest times of the day were set on Pirelli's ultrasoft tyre - a compound which Mercedes are known not to favour and which has not previously been used at Sochi.
It is important not to read too much into Friday times, though. On numerous occasions over the last couple of years Ferrari have looked capable of challenging Mercedes on a Friday, only to drop out of contention in the sessions that matter.
It is well known that Mercedes run conservative engine settings in all sessions bar the final act of qualifying.
However, the margin by which Vettel outpaced the Mercedes - more than half a second - gives some cause for believing that Ferrari could have the edge for real this time.
Sochi is an outright power circuit, which is part of the reason for Mercedes' dominance there. But this year's Ferrari engine looks a match for the Merc, while Hamilton and Bottas's troubles extracting optimum performance right away from the ultrasoft tyres didn't look like a quick fix.
There were clues that Mercedes may have been disguising their pace. At one point in practice Hamilton asked his engineer over the radio whether he had "hit his target" laptime, to which he received the answer that he had.
Bookmakers still make Hamilton favourite to take pole position and to win Sunday's race.
At the prices Vettel is just about worth chancing, but in what should be another close battle, a further bet on the qualifying winning margin falling between a tenth and a quarter of a second is advised.
Vettel leads the championship by seven points after three races having won two events to Hamilton's one, but all three races have been decided by strategy or influenced by safety car deployments.
S Vettel fastest qualifier
1pt 15-8 BoyleSports, Coral, Ladbrokes
Qualifying winning margin 0.1-0.25 seconds
1pt 13-8 bet365