Max Verstappen finished French GP final practice with a whopping 0.7s advantage over Valtteri Bottas as the title leader firmly laid down his marker ahead of qualifying, with Lewis Hamilton adrift down in fifth.
The Red Bull of Verstappen and the Mercedes of Bottas have been evenly matched throughout the weekend but the Dutchman pulled clear with an unexpected margin towards the end of Practice Three - acing the final two sectors to post a 1:31.300 around a fast and tricky Paul Ricard circuit.
The best all other drivers could manage were times in the 1:32s, with Bottas the lead challenger ahead of Carlos Sainz in the Ferrari, and Perez in the other Red Bull.
"Verstappen is so fast out there, it's phenomenal," said Sky F1's Nico Rosberg, with Red Bull having changed setup from Friday to improve straight-line speed.
But Hamilton's Mercedes struggles continued in the hour-long Saturday session, as the world champion couldn't match Verstappen or Bottas on any of the qualifying simulation laps - finishing with a 0.966s deficit to his main title rival.
Qualifying takes place at 2pm on Sky Sports F1, with extensive build-up from 1pm.
"Lewis is really in a bad place at the moment," added Rosberg, with Hamilton having trailed his team-mate in all three sessions so far this weekend.
"So far away from Verstappen, always two or three tenths ahead of Bottas, it's really difficult.
"Mercedes are miles away... let's see if they can find some magic."
Sainz's speed suggests Ferrari, on pole for the last two street races, could be contenders for the top two rows at the very least, although Charles Leclerc was surprisingly off the pace down in 11th in the other red car.
The midfield battle looks to be extremely close heading into qualifying, particularly between McLaren, Alpine and Alpha Tauri with Lando Norris, Fernando Alonso, Esteban Ocon, Pierre Gasly and Daniel Ricciardo in the top-10 in P3.