Valtteri Bottas topped the times for Mercedes ahead of Renault's Daniel Ricciardo in Friday morning's crash-hit opening free practice at this weekend's Russian Grand Prix.
The Finn, who is 55 points adrift of Mercedes team-mate Lewis Hamilton in the title race, clocked a best lap in one minute and 34.923 seconds. This left him half a second clear of the Australian on the smooth-surfaced circuit and six-tenths ahead of third-placed Max Verstappen of Red Bull.
Defending six-time champion Hamilton, who is one win short of equalling seven-time champion Michael Schumacher's career record 91 victories, remained in the Mercedes team garage for much of the session after flat-spotting his tyres and did not clock a truly competitive lap time.
He was classified down in 19th. Sergio Perez was fourth ahead of his Racing Point team-mate Lance Stroll, Esteban Ocon in the second Renault, local hero Daniil Kvyat of Alpha Tauri and Alex Albon in the second Red Bull.
Four-time champion Sebastian Vettel, in his last season with Ferrari, was ninth in the leading scarlet car ahead of Pierre Gasly in his Alpha Tauri. The session was run in bright and warm conditions at the Olympic Park circuit, which was built to host the 2014 Olympic Winter Games.
Bottas soon set the pace, although Perez in his Racing Point briefly interrupted with a fast time. After complaining on Thursday that he was being ostracised, the Mexican settled his differences with the team – which will run in new British racing green livery as Aston Martin next season – after overnight talks.
Ricciardo was briefly top for Renault before Bottas regained the summit while 'black arrows' team-mate Hamilton remained in the garage. Carlos Sainz damaged the rear wing of his McLaren when he smacked the barriers at turn seven after 34 minutes, prompting a Virtual Safety Car period before local hero Daniil Kvyat spun his Alpha Tauri to give the sparse crowd a thrill.
Once the action resumed, at full pace, Canadian rookie Nicholas Latifi crashed his Williams at turn ten, the impact causing the session to be red-flagged. "I crashed," he reported. "I'm ok. Sorry, guys."