Max Verstappen finished a promising fastest for Red Bull on an intriguing opening day of practice at the Belgian GP, while Mercedes were also behind Daniel Ricciardo for surprise-package Renault.
Ferrari, expecting a difficult weekend a year on from dominating at Spa, finished in lowly 15th and 17th positions - a world away from their big rivals of past years.
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Mercedes remain favourites for the weekend but the in-form Verstappen nonetheless hit the front in the afternoon with a best lap of 1:43.744. That was 0.096s faster than Lewis Hamilton, who was the lead Mercedes driver in third.
"Car seems to handle well. It's a good start, but still some things to work on for [Saturday]. But overall I'm pretty happy," said Verstappen after topping a Friday P2 session for the first time since the season's second round.
"I expect them [Mercedes] to be stronger tomorrow. I'm not expecting to fight for pole position, but if we can be closer it'll be good."
It was Ricciardo's second-place finish for Renault which proved the session's biggest surprise. The Australian was just 0.048s back on Verstappen's pace with the RS20 seemingly suiting lower-downforce conditions.
However, Ricciardo did hit problems with 20 minutes to go when he was instructed by the team to park his car up on the side of the track. Renault later confirmed it had been a precautionary measure after the RS20 suffered a loss of hydraulic pressure.
Alex Albon, who has struggled for single-lap pace relative to Verstappen, was a strong fourth in the second Red Bull, just ahead of Sergio Perez with the rapid Racing Points again showing good speed.
Valtteri Bottas had set the morning pace from Hamilton but did not maximise his qualifying simulation and slipped to sixth in P2 ahead of McLaren's Lando Norris and the second Renault of Esteban Ocon.
What's up with Ferrari?
Although their plight at Spa is perhaps not quite as dire as it appeared on Friday's timesheets, Ferrari appear firmly in trouble already in Belgium with their car's straight-line speed deficit exposed.
Charles Leclerc and Sebastian Vettel finished well outside the top 10 in both sessions, with the team 1.3 seconds off the leading pace around the undulating 7km lap.
Whereas Red Bull lapped 1.6s faster than they did in P2 last year, Ferrari were 1.3s slower than they were when they topped the Friday timesheet at Spa in 2019.
In fact, all six Ferrari-powered cars featured among the bottom eight positions - with the works Scuderia squad behind Alfa Romeo.
Ferrari's drivers, who were split by Williams' George Russell, had anticipated a difficult weekend before arriving at Spa.