Lewis Hamilton set the pace in a Mercedes 1-2 but proved he is not infallible as a spin cost him the opportunity to improve his time.
As with Friday’s run on the soft tyres, Hamilton was in a league of his own on Saturday at the new Sochi Autodrom.
The Championship leader posted a 1:38.726, a second quicker than his best from Friday, to easily lead the chasing pack by 0.924s ahead of then second-placed Valtteri Bottas.
However, proving that he is human, he got it all wrong on his next flying lap at Turn 17 and spun, sliding backwards off the track. He avoided the barriers given the huge run-off areas and crawled back into the pits on a set of shot Pirelli soft tyres.
With Hamilton not running in the final eight minutes and the soft Pirellis improving as more laps were put on them, Nico Rosberg moved up to second place, 0.290s down, while Bottas also closed the gap to 0.371s.
Both drivers best times were set on the seventh lap on the soft tyres, although not all seven laps were fast laps.
Daniel Ricciardo put in a late improvement to finish fourth ahead of Felipe Massa, Daniil Kvyat and the two Ferraris of Kimi Raikkonen and Fernando Alonso.
The session was briefly red flagged when Kevin Magnussen’s MP4-29 suffered what appeared to be a right rear suspension failure.
On his way up to Turn 5, the back of his McLaren suddenly gave way and the Dane did extremely well to prevent his slipping and sliding car from smacking the barriers.
He brought it to a halt on the side of the track and the red flags were waved to help marshals recover the car. The session was red flagged for four minutes.
Problems also for Pastor Maldonado as his E22 suffered an ERS failure and did so while he was in it. Told to carefully jump out, he did just that while his mechanics cautiously went to work on it but only after ensuring they would not be shocked. He completed just 2 laps.
01 Lewis Hamilton Mercedes 1:38.726 15 laps
02 Nico Rosberg Mercedes 1:39.016 +0.290 25 laps
03 Valtteri Bottas Williams 1:39.097 +0.371 20 laps
04 Daniel Ricciardo Red Bull 1:39.755 +1.029 16 laps
05 Felipe Massa Williams 1:39.954 +1.228 22 laps
06 Daniil Kvyat Toro Rosso 1:40.009 +1.283 27 laps
07 Kimi Raikkonen Ferrari 1:40.011 +1.285 20 laps
08 Fernando Alonso Ferrari 1:40.151 +1.425 15 laps
09 Jean-Eric Vergne Toro Rosso 1:40.205 +1.479 26 laps
10 Sebastian Vettel Red Bull 1:40.338 +1.612 21 laps
11 Jenson Button McLaren 1:40.355 +1.629 19 laps
12 Nico Hulkenberg Force India 1:40.669 +1.943 23 laps
13 Sergio Perez Force India 1:40.699 +1.973 26 laps
14 Adrian Sutil Sauber 1:41.146 +2.420 21 laps
15 Esteban Gutierrez Sauber 1:41.520 +2.794 20 laps
16 Romain Grosjean Lotus 1:41.915 +3.189 22 laps
17 Kevin Magnussen McLaren 1:42.436 +3.710 4 laps
18 Marcus Ericsson Caterham 1:43.109 +4.383 11 laps
19 Kamui Kobayashi Caterham 1:43.975 +5.249 12 laps
20 Max Chilton Marussia 1:44.737 +6.011 9 laps
21 Pastor Maldonado Lotus 2 laps