Charles Leclerc resumed his standing as the fastest man at the Russian Grand Prix by topping FP3 by three tenths of a second from Ferrari team-mate Sebastian Vettel.
Leclerc traded P1 with Max Verstappen on Friday, but the Dutchman faded from single-lap contention in Saturday's early session and saw a soft-tyre lap spoiled by a pair of mistakes.
Verstappen went airborne after going over the kerbs and then spun later in the lap, kissing the barriers with his rear wing, to prompt a change ahead of qualifying.
Both Verstappen and team-mate Alexander Albon will serve five-place grid penalties.
It remains to be seen if Mercedes can take the fight to Ferrari in qualifying, with Lewis Hamilton lamenting over team radio that a gap of 1.1 seconds to Leclerc was insurmountable.
Hamilton did manage to close the gap to four tenths by the end of the session, going quicker than Valtteri Bottas for the first time in the weekend.
Home fans will have been disappointed by the sight of Daniil Kvyat pulling over with a second engine issue of the weekend. He was already due to start the race from the back of the grid, but now will not take part in qualifying at all.