Red Bull's Daniel Ricciardo staked his claim to a repeat Azerbaijan Grand Prix victory with the fastest time in Friday practice while Formula One world champion Lewis Hamilton remained off the pace.
Man of the moment after winning in China two weekends ago, the Australian lapped the fast straights and turns of the street circuit with a best time of one minute 42.795 seconds on ultrasoft tyres.
"I think we can still find a little bit more but generally I was happy and I think it's going to be quite a close battle tomorrow and Sunday," said Ricciardo.
"This was all we could ask for today. It is encouraging even if we don't qualify on the front row tomorrow as I think the race car will be very strong."
Ferrari's Kimi Raikkonen was second fastest on a cool and gusty evening, a mere 0.069 slower, with Red Bull's Max Verstappen coming back strongly from an earlier crash with the third best time.
Finland's Valtteri Bottas, who was quickest in the opening session for Mercedes in a time of 1:44.242 that he said was a 'bit messy', was fourth while team mate Hamilton could manage only fifth.
"We're not quick enough. Red Bull's definitely quite a bit ahead and I couldn't match their time today," said Hamilton, who is nine points adrift of Ferrari's Sebastian Vettel after three races. "So we've got some work to do.
"I'm going to be knocking on the door of all the engineers tonight, pushing them. I hope I can get them to make some changes," added the Briton, whose team have yet to win this year.
Ricciardo, winner of a chaotic race in Baku last year, had been a 0.035 of a second slower than Bottas in the first practice.
VERSTAPPEN IN THE WALL
The early story was provided by 20-year-old Verstappen, who had promised to drive faster but with more control after a season littered with collisions and spins.
Instead, the Dutch driver locked up while braking and skidded sideways into the tyre wall with 55 minutes remaining, sitting out the remainder of the session while his mechanics prepared to rebuild the car.
Verstappen was still quicker than Ferrari's Sebastian Vettel, the championship leader he apologised to in China after they collided as the Red Bull was trying to overtake, who was 10th and 11th respectively.
Vettel, winner of the opening two races, appeared to be struggling for grip and spun several times in the late afternoon.
The German had been 2.2 seconds off the pace in the earlier practice, while Raikkonen spent much of it in the garage.
"We didn't really have any problems this morning," said the Finn. "I wanted to have a different set-up and unfortunately it takes a long time because there were things to change."
Mexican Sergio Perez opened his day with a third fastest lap for Mercedes-powered Force India, with French team mate Esteban Ocon fifth in a promising sign for a team with only one point so far this season.
They dropped back to 12th and seventh respectively later in the day, however.
"The work we have done today gives me encouragement and I have a good feeling with the car," said Perez.
"The track conditions at the end of the day saw the temperatures drop quite a lot and that's why we saw drivers making mistakes and running wide. It's going to be tricky during qualifying tomorrow."
The weekend forecast sees windier conditions.
Williams, the only team yet to score, also showed a glimmer of improvement with Russian Sergey Sirotkin eighth in the opening stint.
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