Lewis Hamilton endured a mistake-strewn Friday as Mercedes team-mate Valtteri Bottas finished quickest in both practice sessions ahead of the Russian Grand Prix.
The six-time F1 champion can equal Michael Schumacher's record of 91 wins by taking the chequered flag at the Sochi Autodrom on Sunday, a circuit where the Briton has won four times on F1's six visits.
But after a lock-up in FP1 on the hard tyres, Hamilton followed suit in FP2 on both the soft and medium Pirelli compounds.
The main error unfolded on his second flying lap on the softs, and at a time when he was already top of the timesheet by a fraction of a second over Bottas.
But after purpling the first two sectors, Hamilton locked up his front-left at the sharp Turn 13 right-hander, so ruining his lap.
Following behind, Bottas emulated Hamilton's feat in purpling sectors one and two and was 0.777secs up overall, only to overshoot the exit of the final corner and cut up the grass, but the Finn still managed to finish 0.267s quicker, posting a time of one minute 33.786s.
Aside from the soft-tyre, lower-fuel laps in FP2, throughout Friday the duo were on different run plans, with Hamilton operating solely on the hard tyre in FP1, leaving him down in 19th at the end of that session.
Come FP2, they continued to primarily operate on different compounds around what is a tricky track to master given its medium and low-speed corners, with a handful at 90 degrees.
Renault's Daniel Ricciardo was third quickest, following up his second place in FP1, but with the Australian a staggering second off of Bottas' pace, underlining just how far ahead Mercedes is on this track where it has won all six races.
McLaren duo Carlos Sainz and Lando Norris were a strong fourth and fifth quickest, with the team on the Spaniard's side of the garage doing superbly to turn around his car following a first practice shunt that damaged the crash structure, forcing them to change the entire rear axle.
Racing Point's Sergio Perez was sixth quickest, followed by Max Verstappen in his Red Bull, but with the Dutchman 1.529s adrift, and like Hamilton making a mistake with a spin on a lap in which he had posted his quickest first two sectors.
Ferrari duo Charles Leclerc and Sebastian Vettel finished eighth and 10th quickest, the latter 1.664s down, sandwiching the Renault of Esteban Ocon.
AlphaTauri's Pierre Gasly was 11th, narrowly ahead of the second Red Bull of Alex Albon, followed by Daniil Kvyat on home soil and Alfa Romeo's Kimi Raikkonen, who this weekend equals Rubens Barrichello's record of 322 race starts.
Nicholas Latifi, who had suffered a heavy smash in FP1, also had his team to thank for repairing his Williams, allowing him to finish 15th fastest, just ahead of team-mate George Russell, with the duo two seconds down.
Romain Grosjean in his Haas brought up the rear, finishing 3.339s down.
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