Max Verstappen's unprecedented winning streak in Formula One could be under threat after the Red Bull driver finished only eighth in practice for the Singapore Grand Prix.
Verstappen romped to victory in Italy a fortnight ago to become the first driver in the sport's 73-year history to win 10 consecutive races as he closes in on a hat-trick of world championships.
But under the thousands of bulbs that light up the Marina Bay Street Circuit on Friday, Verstappen ended the day more than seven tenths of a second behind Ferrari pace-setter Carlos Sainz, the Spaniard who took pole position in Monza.
Charles Leclerc finished second for Ferrari as the Italian team completed a practice one-two, with George Russell third for Mercedes, 0.235 sec adrift.
Aston Martin's Fernando Alonso was fourth, with Lewis Hamilton fifth in his Mercedes, one place ahead of McLaren's Lando Norris.
Oscar Piastri had an ordinary day, finishing 19th in the opening session and 15th in the second.
Red Bull are unbeaten this season, but they did not have a car inside the top six on Friday, with Sergio Perez, who triumphed here last year, seventh.
Verstappen, who has won 12 of the 14 rounds so far, has not lost a race since the Azerbaijan Grand Prix on April 30.
But the Dutch driver has never triumphed in Singapore and suggested ahead of Friday's running that the high-downforce, low-speed nature of the city-state track could play into the hands of Red Bull's rivals.
While times in practice must be treated with caution as teams trial varying fuel loads and tyre strategies, it is Ferrari who hold the upper hand heading into qualifying on Saturday at a track where overtaking is notoriously difficult.
Indeed, eight of the 13 races here have been won from pole. Although the removal of turns 16 to 19 in favour of one long straight could improve the action for Sunday's 62-lap race.
"Ferrari are fast and we are just way worse than we expected," said Verstappen.
"We were struggling with the balance, and we never got the car together so there are a few things for us to figure out. We will try to improve but it is a big gap."
While the second running passed off without major drama, the opening session was disrupted on three occasions when a lizard invaded the three-mile circuit.
Verstappen was the first to report the reptile at turn nine midway through the running.
"There is a lizard on track again," said the Red Bull driver, who had a similar encounter here back in 2016. "It is a smaller one this time."
Verstappen's race engineer Gianpiero Lambiase replied: "Maybe Godzilla has had a kid." There was a second interruption, and then a third, as yellow flags were deployed.
"Another lizard, but a different one this time," said Russell.