Max Verstappen and Red Bull would surprisingly set the pace, as the Dutchman led both practice sessions ahead of the Azerbaijan Grand Prix on Friday.
He would set the bar at 1m43.362s on the supersoft tyres during the afternoon, on a day that saw Ferrari and Mercedes both lack the invincibility they have shown throughout this Formula 1 season.
Valtteri Bottas would be Verstappen's closest challenger in his Silver Arrow, exactly a tenth behind the 19-year-old, but Red Bull does appear the team to beat heading into the weekend as Daniel Ricciardo was P2 behind his team-mate in the morning and would pretty much match Bottas in the second 90 minutes of running.
Ferrari was steady if not spectacular throughout the day, Kimi Raikkonen and Sebastian Vettel would be fourth and fifth at the checkered flag but the German did seem to struggle more than most under braking taking to the escape roads of multiple occasions across both sessions.
Lewis Hamilton, who had issues last year in Baku, may be enduring a repeat this year, finishing 10th in the afternoon, though would not complete a qualifying-style run on the supersoft tyres, due to a crash for Jolyon Palmer causing the second of two red flags on Friday.
Sergio Perez was the first man to do so, after a heavy crash at the tight Turn 8 with around 20 minutes left in Practice 1. The Mexican would finish fourth in that session, however, and seventh again in Practice 2, as Force India continued their pace from Canada, emerging definite top eight contenders.
Also having a good day was Lance Stroll in the Williams, finishing the day in sixth place overall. The Canadian scored his first points at his home race two weeks ago and was pleased with the setup of his car as he finished ahead of team-mate Felipe Massa.
Finally, Daniil Kvyat had a quietly good day, achieving top 10 positions in both sessions and ahead of Toro Rosso team-mate Carlos Sainz at a circuit where the non-Mercedes powered midfield teams may need trouble ahead if they want to fight for points on Sunday.
It was another troubled day at McLaren, as yet another Honda engine failure curtailed Fernando Alonso's running in the afternoon. It was certainly not a good start to a weekend that is set to be very difficult for the British team, as engine-related grid penalties will see both the Spaniard and Stoffel Vandoorne start at the back of the grid on Sunday.
Though the sight of F1 cars locking up into escape roads was common on Friday, Romain Grosjean suffered more than most as Haas' perennial weakness was on full display. The Frenchman changed material after a troubled start to Practice 2 but then further inconsistencies with the brake-by-wire saw Romain left incredibly frustrated.
He was at the bottom of the timesheets when the action ended, with his team-mate Kevin Magnussen only 14th for the American team.
The streets of Baku don't suit Renault and it showed with Nico Hulkenberg only 15th, a place ahead of Palmer who, as mentioned, ended his day in the barrier after repeating Perez's morning crash at Turn 8.
And Sauber, though not absolute slowest, again brought up the field with Pascal Wehrlein 18th and Marcus Ericsson 19th, as the Swiss team continue to deal with the fallout after losing team boss Monisha Kaltenborn on Wednesday.
A hectic Friday with many drivers with plenty of analysis and work to do overnight, none more so than Hamilton, with the ghosts of Monaco reappearing, and Ferrari who can see the opportunity to capitalise if they can overcome the unexpected challenge of Verstappen in his RB13.
