Max Verstappen concluded the weekend's only practice session in Baku at the top of the timesheet, the Red Bull charger leading Ferrari's Charles Leclerc and teammate Sergio Perez.
It was a disrupted workout for the field however, with a flurry of yellow flags and a ten-minute red flag neutralization. Alpine was a victim of its own reliability issues, with Pierre Gasly and Esteban Ocon achieving only an aggregate 15 laps for the team.
Over at Mercedes, Lewis Hamilton and George Russell both suffered brake issues in the early part of their session, the pair clocking in outside of the top ten.
Formula 1's new Sprint format which has been introduced this weekend has left drivers with just a single 60-minute practice session to set up their cars for this afternoon's race qualifying, while tomorrow's schedule will feature another qualifying shootout in the morning and the Sprint event in the afternoon.
Due to the limited practice time and with a raft of updates to test for almost every team, track action was frantic from the outset when the lights went green at the start of FP1.
Flying laps were the norm in the early stages of the session and so were off-track excursions, with a flurry of yellow flags displayed at regular intervals.
But the messy start turned outright chaotic, with AlphaTauri's Yuki Tsunoda spinning and suffering a puncture and then Pierre Gasly grounding to a halt, the rear end of his Alpine ablaze.
Meanwhile, Haas' Kevin Magnussen was also seen stopped at Turn 1, the victim of a fuel pressure issue.
The wide-spread commotion brought out the red flag while the clock continued to tick.
At that point, Verstappen topped the timesheet, followed by Perez, Ferrari's Leclerc, Sainz and Alpine's Esteban Ocon.
There were complaints in the Mercedes camp by both Lewis Hamilton and George Russell about the W14's brakes.
The session resumed with less than 30 minutes left on the clock. But the nightmare continued for Alpine, with Ocon exiting his car and calling it a day following a technical issue, leaving the French outfit in the dark with virtually zero data collected ahead of qualifying.
The leaderboard remained unchanged among the top three, but Stroll and an impressive de Vries slotted in fourth and fifth, although they were both dispatched in short order by Sainz.
But just as everyone regrouped with 15 minutes to go, Stroll pressed on and snatched second, just 0.219s behind Verstappen, the Aston charger splitting the two Red Bulls.
However, Williams' Alex Albon took full advantage of his car's low drag to leapfrog ahead of Verstappen.
But the Dutchman, also shod with the soft tyre, immediately responded with a 1m43.042s that put him ahead, at least until a 1m42.651s flyer from Perez allowed the Mexican to steal his teammate's thunder.
With a little over than five minutes to go, Leclerc seized P2, slotting his Ferrari between the bulls. But the Monegasque went one better in the final minute of the session.
Unfortunately, the Scuderia driver's effort was bettered by 0.037s by Verstappen who thus concluded the single practice session of the weekend in first place.
Behind the Dutchman followed Leclerc, Perez an Sainz while McLaren's Lando Norris rounded off the top five.
De Vries cleverly exploited his AlphaTauri car's low drag and top speed to clock in sixth ahead of Stroll, Alonso, Albon and Alfa Romeo's Zhou Guanyu.
Over at Mercedes, it was a lacklustre session in terms of performance, with Hamilton – who ran only on the medium tyre – and Russell concluding FP1 respectively P11 and P17.
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