Valtteri Bottas secured pole position in the Mexican Grand Prix with teammate Lewis Hamilton joining him on the front row.
The result on Saturday could prove hugely influential in the 2021 title race, with Max Verstappen's 12-point drivers' championship lead under threat.
The Finn, in his last few races for his current team, put in an outstanding time of 1:15.875 seconds.
Formula 1
'Mercedes had no grounds for complaint' - Horner
17/12/2021 AT 09:49
In second with 1:16.020 was current champion Hamilton in his Mercedes.
Red Bull's Verstappen - fastest at the end of FP2 on Friday evening - was third with 1:16.225, just ahead of his teammate, Sergio Perez, driving in his home country.
After Sunday's GP there are just four more to go in the race calendar. The tour moves on to Brazil, before decamping to the Middle East to run through Qatar, Saudi Arabia and then Abu Dhabi.
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The UCI Track Champions League is coming and you can watch all of the action live on the Eurosport app, and discovery+. Find out more about the "mind-blowing" new era for track cycling, with the first event on November 6 in Mallorca.
Formula 1
Verstappen: 'I don't feel sorry for Hamilton'
17/12/2021 AT 08:47
Abu Dhabi Grand Prix
'No assurances' Hamilton will race next season, says Mercedes boss Wolff
16/12/2021 AT 13:13