Lewis Hamilton and Mercedes are staring at being comprehensively out-qualified by Red Bull following a crushing final practice session for the Mexico City Grand Prix.
But it was not Max Verstappen who led the way, instead it was team-mate Sergio Perez, raising home hopes of pole position from their hero at the Autodromo Hermanos Rodriguez.
Perez finished with a time of one minute 17.024s, almost two-tenths of a second quicker than Verstappen, with Hamilton a staggering 0.651s off the pace.
When told of the gap late on, a clearly puzzled Hamilton replied: "Six and a half tenths?", with the reigning champion at a loss to understand the deficit.
Unfortunately, due to an oil spillage on the track through turn four from a support race ahead of final practice, it resulted in a slow start to the session as the majority of the drivers were reluctant to play 'roadsweeper'.
AlphaTauri's Yuki Tsunoda was the first to take to the track and quickly reported the surface to be "slippery" despite the FIA's attempts to cover the spillage with cement dust.
The corner proved problematic through the session, resulting in Verstappen taking to the track last and with only 30 minutes of the hour-long run remaining.
The championship leader, by 12 points over Hamilton, made it count immediately by setting the fastest lap at that stage by four-tenths of a second over Perez with a time of 1:17.537s.
After Valtteri Bottas moved to within two-tenths of a second of Verstappen, the Dutch driver then delivered a stunning lap of 1:17.217s to move half-a-second clear of the Finn.
On a brand new set of tyres late on as the drivers ran their qualifying sims, seven-time champion Hamilton could only muster a time just under seven-tenths off Verstappen.
There was an improvement on his second attempt after a couple of cool-down laps before Perez then sent his home fans into a frenzy with his hot lap.
Verstappen struggled on his final set of soft tyres and failed to find any improvement, leaving Perez out in front.
Bottas finished fourth quickest, 0.684s adrift, followed by Ferrari's Carlos Sainz again fifth fastest but a second back.
Ricciardo showed considerable improvement from his Friday performance to set the seventh-best time, followed by AlphaTauri's Pierre Gasly, the second Ferrari of Charles Leclerc and then Norris rounding out the top 10, 1.288s down.
With the top five covered by a second, from Sainz in fifth down to 16th-placed Ocon, there was just under a second, highlighting the strength of Red Bull, in particular, and Mercedes.
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