Sebastian Vettel and Ferrari laid down their marker ahead of qualifying by topping the timesheet in final practice at the Azerbaijan GP.
Despite only managing 10th and 11th in Friday's two sessions and struggling with his car's balance, Vettel went fastest with a 1:43.091 in Practice Three - finishing three tenths of a second ahead of Lewis Hamilton in the Mercedes.
But while Hamilton was just ahead of Kimi Raikkonen in the sister Ferrari, Max Verstappen in the Red Bull as well as team-mate Valtteri Bottas, he was still not happy with his setup and Mercedes still look off the pace ahead of a crucial qualifying hour.
The shootout looks all the more intriguing as Red Bull, who dominated on Friday, kept their cards close to their chest in P3. Max Verstappen hooked up a late lap to go fourth, 0.428s off Vettel's benchmark, while the in-form Daniel Ricciardo finished down in 12th and almost two seconds off the pace.
"We're going into qualifying and we're not really sure who has the most potential," said Paul di Resta, who also predicted Ferrari had been sandbagging on Friday.
Many drivers were struggling for grip in the slippery and windy conditions in Baku, and a heavy shunt for Sergey Sirotkin in the Williams caused a red flag towards the end of the session.
The Russian rookie couldn't find enough grip around Turn Three and almost lost his front right tyre through the impact with the barriers, with his team now facing a speedy turnaround to get his car ready for qualifying.
It was another promising session for Williams apart from that, however, with both drivers in the top 10 and Lance Stroll in eighth.
That's one of the reasons it looks set to be an incredibly tight battle to make Q3 in qualifying. Force India are looking the most likely with Sergio Perez sixth and best of the rest, and Esteban Ocon ninth.
Kevin Magnussen was seventh for Haas, though team-mate Romain Grosjean was complaining about his car's brakes throughout and nearly had a crash of his own.
McLaren's leading car was once again that of Fernando Alonso. The Spaniard was 11th and 1.6s off the leading time, while Stoffel Vandoorne struggled won in 18th.
Renault, meanwhile, chose to set their fastest times on supersofts - Carlos Sainz and Nico Hulkenberg finished 16th and 17th respectively - but will expect to improve once the shootuout begins.
Will Ferrari continue to impress after a strong start to Saturday? Will Mercedes recover? Were Red Bull holding back in P3 and can they challenge? Who will make Q3? Find out in qualifying, with the hour-long build-up show starting at 1pm on Sky Sports F1.