Lewis Hamilton finished only seventh in second practice for the Mexican Grand Prix as Max Verstappen completed a practice double.
Verstappen, 21, vowed to deny Hamilton the chance of securing his fifth championship in style, and the Dutchman appears the man to beat after a dominant day for his Red Bull team.
He was fastest in the opening running at the Autodromo Hermanos Rodriguez, and led the way later in the day, too, with Red Bull boasting a mighty one-second advantage over the rest of the field.
But there was a sour end to both his, and Red Bull’s, impressive day after the team’s temperamental reliability issues struck again.
Verstappen broke down following an engine problem in the closing 10 minutes, and had to hitch a ride on a scooter back to the pits.
Daniel Ricciardo was just 0.153 seconds shy of his teammate, while Carlos Sainz finished an impressive third for Renault, albeit 1.2 seconds off the pace.
Hamilton, who will secure the title with two rounds to spare by finishing seventh on Sunday, was comfortably off the pace in both sessions.
The Briton complained about losses of power to his Mercedes machinery in the opening running, and then later about his tyres. He finished a distant seventh, 1.4 seconds off Verstappen.
Ferrari’s Sebastian Vettel must take the chequered flag to stand any chance of denying Hamilton the title, but he failed to trouble the top of the order here.
The German, 70 points behind Hamilton with only 75 to play for, finished fourth, 1.23 seconds slower than the speedy Red Bulls.
The Mexico City circuit sits 2,200 metres above sea level and the high altitude acts as an equaliser in engine performance.
Therefore, the Renault in the back of Verstappen’s Red Bull – usually inferior to the might of Mercedes and Ferrari – is on a more competitive playing field this weekend.
Yet, while Red Bull will be encouraged by their impressive pace, the mechanical problems which have plagued Verstappen’s teammate Ricciardo in recent races, reared their head on his car, which will no doubt be a cause for concern.
The Renault factory team have been well off Mercedes, Ferrari and Red Bull this season, but Sainz and teammate Nico Hulkenberg, who finished fifth, could be contenders in Mexico after their surprise pace in practice.
A mention, too, for Brendon Hartley who finished sixth for Toro Rosso.
Four of the top-five placed cars use Renault engines, but McLaren – the other team on the grid who are powered by the French manufacturer – were nowhere to be seen.
Fernando Alonso finished last-but-one of the 20 runners, while his teammate Stoffel Vandoorne was only marginally better off in 15th.
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