George Russell finished fastest in second practice for the Miami Grand Prix as Max Verstappen broke down in his Red Bull.
In the sweltering heat, Russell was 0.106 seconds clear of championship leader Charles Leclerc, with Sergio Perez third and Lewis Hamilton fourth, while Carlos Sainz’s poor run of form took another sorry twist when he crashed out in his Ferrari.
Formula One is in Miami for the first time, at a 3.36-mile circuit constructed around the Hard Rock Stadium, 15 miles north of the city.
Mercedes have brought a number of upgrades to America – including a new low-drag rear wing and revised front wing – in a bid to reverse their early-season problems.
And the early signs are positive, with Russell improving on second in the opening running to post the day’s fastest time. Hamilton, 58 points behind Leclerc in the standings, was 0.241 sec adrift of his team-mate.
“We don’t really understand it,” said Russell. “We have hit the ground running.
“We knew the conditions would suit us better here because this is the first real hot race of the season, and that has helped us, but it is only Friday and we are not getting carried away.
“But it has definitely been a productive day for us, and probably the most productive Friday we have had this year.”
Hamilton added: “Practice is just practice and everyone is doing something different – not everyone is showing their true pace.
“But we seem to be quicker here. We have improved in some way, I am not sure where that is because we still have the bouncing.
“There are definitely positive elements to take from today. I am still struggling with the car but George looked fast out there.”
Verstappen dominated in Imola a fortnight ago to get his championship defence back on track.
But Red Bull’s mechanical woes, which saw the Dutchman retire from two of the opening three races, reared their head again on Friday.
The world champion missed the opening chunk of the one-hour running following a gearbox change, and when he eventually emerged on track, his rear brakes overheated and he was forced to limp back to the pits.
“It’s s***,” said Verstappen on the radio. “I couldn’t f****** steer. I cannot do anything. I’m really sorry.”
Team principal Christian Horner was seen shaking his head on the Red Bull pit wall.
Over at Ferrari, there was further disappointment for Sainz. The Spaniard crashed out on the opening laps of the past two rounds in Melbourne and Imola, and then suffered a front-right puncture in the first action after losing control of his Ferrari through Turns 4 and 5 and limping back to the pits.
But worse was to come for Sainz later in the day when he carried too much speed through Turn 13 and hit the wall.
Sainz sustained significant damage to the front-left of his machine with the action suspended to retrieve his stricken car. A second red flag was deployed when Nicholas Latifi stopped with a mechanical failure.
Elsewhere, double world champion Fernando Alonso finished fifth, one spot ahead of British driver Lando Norris. Valtteri Bottas failed to complete a lap following damage sustained to his Alfa Romeo in the opening running.