Carlos Sainz beat team-mate Charles Leclerc to the fastest time as Ferrari dominated Practice Two at the French GP to continue their world championship resurgence.
Sainz produced a 1:32.527 to edge Leclerc by 0.1s, with world championship leader Max Verstappen a notable half-second back from the Spaniard's leading time, while his Red Bull team-mate Sergio Perez could only manage 10th.
The performance will give Ferrari confidence about extending their streak of back-to-back victories, with Leclerc's win at the Austrian GP two weeks ago having narrowed Verstappen's world championship lead to 38 points.
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However, Sainz's success will be tempered by confirmation earlier on Friday that he will take a 10-place grid penalty for Sunday's race, after taking a new Control Electronics following an engine failure last time out in Austria.
Mercedes, who welcomed back Lewis Hamilton after the seven-time world champion sat out Friday's opening session, were unable to live up to the high expectations many had for them coming into the weekend. Hamilton was fifth, with team-mate George Russell fourth as they failed to match Ferrari's pace despite the introduction of new upgrades.
Lando Norris delivered an encouraging sixth-placed finish, with Pierre Gasly and Kevin Magnussen separating he and McLaren team-mate Daniel Ricciardo.
Horner: I think it will be tight
Ferrari's dominant showing in Practice Two came after Leclerc had edged Verstappen earlier on Friday, with the Dutchman's deficit in the second session coming as something of a surprise.
Pace has rarely been a problem for Ferrari throughout the 2022 season, with reliability having cost the Italian team on several occasions - most recently when Sainz's engine failed in Spielberg.
There were concerning signs in Friday's first session when Leclerc complained of a technical issue, but it appeared to be smooth sailing from there on as both cars consistently produced without trouble.
It remains to be seen whether Sainz's prospective 10-place grid penalty will be increased, with there being some expectation that he could choose to take further engine parts and drop to the back of grid.
Speaking to Sky Sports F1 after the session, Red Bull team principal Christian Horner insisted that he wasn't concerned by the gap and expects another tight battle with Ferrari for the remainder of the weekend.
Horner said: "I think they're looking quick but I take real comfort from, if you have a look at that last little run there over a five-six lap period, I think we're closer.
"It's been so tight between the teams in the first 11 races, I've got no reason to believe it's going to be really that much different here.
"It's going to be getting it right, tyre degradation, strategy. Qualifying isn't quite the premium that it is at other circuits because you can overtake, but you've got to be on the first couple of rows."
Mercedes upgrades fail to make impact
Expectations had been high for Mercedes coming into Friday, with the smooth nature and layout of the Paul Ricard Circuit expected to suit the Silver Arrows, who have shown signs of improvement in recent weeks and were also welcoming new upgrades in the south of France.
Hamilton sat out the first session as Nyck de Vries fulfilled one of the team's two young driver sessions for the season, but was unable to make a major impact as he returned later in the day.
Russell was 0.7s back from Sainz's leading effort, while Hamilton was almost a full second behind the Spaniard, with those margins similar to the deficit Mercedes have faced all season as they've struggled to adjust to F1's new design regulations for the 2022 campaign.
While being off the pace has become the norm for the eight-time reigning constructors' champions this season, recent improved performances and optimism over their chances at the circuit may make this latest disappointment one of the hardest to take.
"We're probably a little bit further off the pace today than we would have hoped," Hamilton said.
"We have a lot of work to do, a lot of ground to cover still. The car is not spectacular here, I don't know why, but overnight we usually make a bit of a step so I'm hoping that's the case tomorrow."
Speaking to Sky Sports F1 between Friday's two practice sessions, Mercedes team principal Toto Wolff said: "(It was) not where we want to be. We're trying lots of parts but we're just lacking pace at the moment in the free practice session.
"We have a few aerodynamic modifications on the floor, on the side edges - little things that should make it better."