Lewis Hamilton finished only 17th in practice for the Italian Grand Prix as Sergio Perez crashed out.
Carlos Sainz provided Ferrari’s home fans with reason for cheer by posting the fastest time at the Italian team’s home track in Monza.
The Spaniard, who celebrated his 29th birthday on Friday, edged out McLaren’s Lando Norris by 0.019 seconds with championship leader Max Verstappen in fifth place, two tenths back.
But seven-time world champion Hamilton, who signed a new £50million-a-year contract with Mercedes earlier this week, ended up only 17th of the 19 drivers who set a time after bemoaning the lack of straight-line speed.
Hamilton’s Mercedes team-mate George Russell finished ninth, 0.821sec slower than Sainz.
While Verstappen has romped to 11 wins from 13 this season – and could become the first driver in history to seal 10 consecutive victories on Sunday – his team-mate Perez has endured a turbulent campaign.
And the Mexican faced more misery here after he lost control of his Red Bull machine through the high-speed Parabolica.
Perez ran on to the gravel on the exit of the corner leading into the main straight and skidded across the sandtrap before nudging the wall.
Perez was able to limp back to the pits but team principal Christian Horner was left grimacing on the Red Bull pit wall.
Before his spin, Perez had displayed encouraging pace – finishing third, 0.185 behind Sainz – and unusually ahead of Verstappen.
Verstappen, 138 points clear in the world standings on his unstoppable march towards a hat-trick of titles, ended the opening running at the top of the time charts. But his best effort in the day’s concluding running was scuppered by traffic.
The 25-year-old wanted to go for another timed lap, only for his race engineer Gianpiero Lambiase to tell him “it isn’t qualifying”.
The Dutch driver was also fined 500 euros (£428) for breaking the 50mph pit-lane speed limit by 3mph.
However, given his crushing dominance this year, he will head into the remainder of the weekend as the favourite to land another win and better the record he shares with Sebastian Vettel.
McLaren have bounced back from a poor start to the year following an upgrade at June’s Austrian Grand Prix. Behind Norris in second place, Oscar Piastri finished fourth.
Elsewhere, Charles Leclerc, who won here to the delight of the Tifosi in 2019, was sixth, one place ahead of the ever-impressive Alex Albon in his Williams, with Fernando Alonso eighth for Aston Martin.
Alonso’s team-mate Lance Stroll failed to set a lap after he broke down with a fuel system failure in the opening moments.
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