Charles Leclerc pipped Sergio Perez in a tight second practice session for the Azerbaijan Grand Prix as title contenders Max Verstappen and Lando Norris were off the pace.
Leclerc was the last driver to do his qualifying simulation and benefited slightly from the faster track conditions to edge out Perez by 0.006s, with Lewis Hamilton in third at only 0.066s behind the Ferrari driver.
Championship leader Max Verstappen was only sixth and 0.545s adrift of Leclerc and Norris didn't complete a fast lap on the softs due to traffic.
Verstappen holds a 62-point lead over Norris with eight events remaining and Perez's speed suggests they should be more competitive this weekend compared to recent races.
But Perez was happier with the car on Friday in Baku as Verstappen complained about understeer and nearly hit the wall with a lock up at Turn Five.
As for Norris, he was on course to be just ahead of Verstappen in second practice but came across Pierre Gasly at the flat-out final sweeping corners.
Gasly tried to get out of the way due to a battery issue but forced Norris to back out in a scary moment for both drivers.
The McLaren driver would have been somewhere around Carlos Sainz in fourth, Oscar Piastri in fifth and Verstappen in sixth, with all three drivers half a second behind pace-setter Leclerc.
Instead, Norris ended up down in 17th and will be hoping McLaren can find time overnight ahead of final practice at 9.30am on Saturday, which is followed by qualifying at 1pm, live on Sky Sports F1.
Too close to call in Baku
The close battle on Friday is a continuation of F1's extremely competitive races during the European leg of the season, with six different winners in the last seven Grands Prix.
Hamilton looked the better of the two Mercedes in the second session, despite a hot seat, which was also an issue in Monza.
The seven-time world champion has admitted to struggling in Qualifying but will be buoyed by his strong pace on Friday on a track where one-lap pace is important.
"It's not just Leclerc and Perez, for Lewis it was also a great day," said Sky Sports F1's Karun Chandhok.
"It underlines what we've been saying all day, the top four cars are in this fight.
"It's going to be unbelievably close. I think Qualifying is going to be absolutely sensational."
Elsewhere, Mercedes' George Russell was forced to change his engine ahead of second practice and also had a sensor issue, so missed out on some track time as he finished the session in ninth.
British teenager Oliver Bearman was 10th behind Russell and Haas team-mate Nico Hulkenberg in second practice.
Bearman, 19, is in Kevin Magnussen's seat this weekend's as the Dane is banned due to hitting the limit for penalty points. Magnussen will return in Singapore next week.
Aston Martin's Lance Stroll was seventh and Fernando Alonso was 12th, with several drivers taking trips down the Baku City Circuit run-off area but managing to avoid the wall, unlike Leclerc and Franco Colapinto in first practice.
Sky Sports F1's live Azerbaijan GP schedule
Saturday September 14
9.15am: Azerbaijan GP Practice Three (session starts 9.30am)
11.10am: F2 Sprint
12.15pm: Azerbaijan GP Qualifying build-up
1pm: AZERBAIJAN GP QUALIFYING*
3pm: Ted's Qualifying Notebook
Sunday September 15
8.30am: F2 Feature Race
10:30am: Grand Prix Sunday: Azerbaijan GP build-up*
12pm: The AZERBAIJAN GRAND PRIX*
2pm: Chequered Flag: Azerbaijan GP reaction
3pm: Ted's Notebook
*also live on Sky Sports Main Event
Formula 1 leaves mainland Europe for Baku and the Azerbaijan Grand Prix this weekend, live on Sky Sports F1. Stream every F1 race and more with a NOW Sports Month Membership - No contract, cancel anytime
