Charles Leclerc was quickest in this morning's final practice session, which like yesterday was compromised by the track being damp following overnight rain. Indeed, it was only in the final 13 minutes of the session that the drivers were able to switch to slicks.
Though qualifying, like FP2 yesterday, should be held in much improved conditions, it is expected that there will be further rain tonight and possible during the race tomorrow, which will only add to the teams' preparation issues.
On the back of its disqualification from the Japanese Grand Prix, the last thing that Renault needed was the cooling system "pollution" issue which sidelined both cars earlier.
With the United States Grand Prix a week away, a number of teams are thought to be concerned at the lack of spares, a situation not helped by the changeable conditions, with Red Bull understood to be particularly affected.
Ahead of Q1, the air temperature is 18.3 degrees C, while the track temperature is 32.2 degrees. Other than being unseasonably cool it remains somewhat overcast, though the sun is attempting to break through, with a 10% chance of rain.
The lights go green and Russell gets things underway, followed, shortly after, by his Williams teammate.
As he starts his flyer, Russell reports that his tyre temperatures are still low. He subsequently posts a 33.152, with Kubica posting a far more sensible 20.313 moments later.
On his second lap Russell improves to 19.547, as Vettel is among the drivers heading out for their first run.
Grosjean is an early spinner at Turn 1, the Haas driver locking up the rear of the car and losing the rear end.
Kvyat goes quickest but is instantly demoted by Norris and then Raikkonen, the 40-year-old posting 17.626.
A 16.859 sees Vettel go top as Leclerc locks-up in Turn 13. The Monegasque goes second as Albon goes top with a 16.175.
Hamilton goes second with a 16.424, but is demoted when Verstappen goes quickest with a 15.949.
Bottas goes sixth (17.062), ahead of Raikkonen, Gasly, Sainz and Ricciardo.
The Haas duo go 17th (Magnussen) and 18th, the American team never enjoying success here.
Hamilton is one of several drivers to remain out, Albon is another. The Briton posts PBs in the final sectors but fails to improve on his previous best.
With 2:20 remaining, the drivers head out for the final assault.
Russell improves to 18th, as Norris goes 8th and Hulkenberg 10th. Both are demoted however when Kvyat goes sixth.
Raikkonen goes 11th, while Alfa teammate Giovinazzi goes 15th.
"Argh! I had no grip," complains Stroll.
"Unbelievable," says Grosjean, the Haas driver at a loss to explain to drop off in performance since this morning.
Quickest is Verstappen, ahead of Albon, Leclerc, Hamilton, Vettel, Kvyat, Sainz, Bottas, Gasly and Norris.
"At the moment everyone is on the soft tyres, but the crucial session will be Q2," says Pirelli, "when the medium tyre is likely to be the one to have." Indeed.
Sainz is first out for Q2, followed by Sainz and Gasly, all three are on mediums, as are the Mercedes pair and the Ferraris.
Kvyat posts 17.712 and Gasly 18.159, as it is revealed that the Russian and Ricciardo are to be investigated for a pitlane incident.
A 16.481 sees Hamilton go top as Bottas aborts his lap after running wide in the stadium.
Vettel goes quickest with a 15.914, with Leclerc second on 16.219.
Moments later, Verstappen splits the Ferraris with a 16.136, as Albon goes fifth, ahead of Hulkenberg and Norris.
Albon is told to work his tyres in "7, 8, 9 and 10".
As Perez begins his first flyer, the crowd roars.
"Sometimes it feels like the car is on the handbrake," says Albon, which is exactly what Verstappen said yesterday.
A 16.981 sees Perez go seventh, as Hamilton makes a mistake in Turn 11. "These tyres are ****," says the Briton.
Bottas improves to fourth with a 16.398, just ahead of his Mercedes teammate.
Ahead of the second runs, Sainz, Giovinazzi, Raikkonen and the Toro Rossos comprise the drop zone, the latter clearly needing to switch to the softs as their medium pace isn't good enough.
Perez, in seventh, Hulkenberg, Norris, Ricciardo and the Alfa pair all sets their times on the softs.
"The car just wasn't great on that tyre," says Hamilton, as he asks if the others were on the mediums also.
Indeed, only the Mercedes pair are on the yellow-banded rubber. A bold move from the world champions.
Sainz improves from 11th to fourth with a 16.267, thereby demoting the Mercedes pair.
Gasly goes eighth and Norris sixth, but both are demoted when Bottas goes quickest with a 15.852 and Hamilton posts a 15.721.
Both Renault drivers fail to make the cut, as does local hero Perez.
Quickest is Hamilton, ahead of Bottas, Vettel, Verstappen, Leclerc, Sainz, Norris, Albon, Kvyat and Gasly.
We lose Perez, Hulkenberg, Ricciardo, Raikkonen and Giovinazzi.
Check out our Saturday gallery from Mexico City, here.
Norris is first out for Q3, followed by the Toro Rossos and his McLaren teammate.
The Ferraris and Bulls head out in a pack, seemingly having learned nothing from Monza.
Norris posts 17.432, but this is soon beaten by Kvyat, Gasly and Sainz (16.743).
Bottas and Vettel trade fastest sector times, the Finn crosses the line at 15.338, and as Hamilton posts 15.290, Vettel crosses the line at 15.170.
However, Verstappen bangs in a 14.910, with Leclerc taking second with a 15.024, 0.114s off the pace.
"It's a good banker," the Dutchman is told.
A 15.336 sees Albon go 5th, thereby splitting the Mercedes pair.
With 2:38 remaining the final assault gets underway. Vettel follows Bottas down the pitlane, with Verstappen the last to head out.
While Vettel allows Bottas to pull away, the Finn closes up on Leclerc.
PBs from Leclerc and Albon, indeed only Vettel fails to improve in the opening sector.
Leclerc goes wide in Turn 7, as Hamilton goes quickest in S2.
However, Bottas goes off in the final corner and brings the session to an immediate end.
Asked if he is OK, after what was a heavy clash with the barriers, Bottas is clearly winded.
As a result Verstappen has pole, ahead of Leclerc, Vettel, Hamilton, Albon, Bottas, Sainz, Norris, Kvyat and Gasly.
Perez is eleventh, ahead of Hulkenberg, Ricciardo, Raikkonen, Giovinazzi, Stroll, Magnussen, Grosjean, Russell and Kubica.
Bottas climbs from his car as the medical car is deployed. Replay shows the Finn losing the car at the start of the final corner and careering along the barriers before being brought to a sudden halt by the Tecpro barrier.
So, twelve months after losing out to his teammate, Verstappen takes pole in Mexico, setting himself up perfectly for a third successive win here.
However, the Ferraris will not be making life easy for him tomorrow, and he and Vettel have clashed in Turn 1 previously.
Starting on the mediums it will be interesting to see how Mercedes fares, while any significant damage to Bottas' car could aid his teammate's quest to wrap up the championship here once again.
Both McLarens and Toro Rossos in the top ten, for what should be an interesting race, especially if the weather gods decide that they want to play.
Kvyat could yet face a penalty following his silliness in the pitlane in Q1, while Verstappen could face sanction for not backing off in the final sector of his final lap despite the yellows as a result of Bottas' crash.
As is so often the case, we may yet see the stewards play a bigger role in the weekend's events than we would wish.
Check out our Saturday gallery from Mexico City, here.