Lewis Hamilton's quest to secure a sixth world championship in Mexico received a controversial boost on Saturday night after Max Verstappen was stripped of pole position.
Verstappen was dealt a three-place grid penalty for failing to slow under yellow flags following Valtteri Bottas' last-corner crash. The Dutchman's punishment moves Hamilton up to third on the grid.
Hamilton must finish at least on the podium here on Sunday to stand any chance of taking the title. Charles Leclerc assumes pole with Sebastian Vettel forming an all-Ferrari front-row.
Hamilton will win the championship at the Autodromo Hermanos Rodriguez if he outscores Mercedes team-mate Bottas by 14 points.
Bottas is expected to start from sixth despite sustaining extensive damage to his car.
The stewards initially chose not to investigate Verstappen, but launched a probe following comments made by the Dutchman in the post-qualifying press conference.
Asked if he had slowed down to acknowledge the yellow flags deployed after Bottas' accident, he replied: "Didn't really look like it, did it? No."
Verstappen was then called before the stewards - and more than three hours after securing only the second pole of his career, he was pushed back to fourth. Verstappen was also hit with two penalty points on his licence.