Sainz was only 0.018 seconds faster than his teammate, who was on track to win but lost time in the final sector.

Mercedes driver George Russell finished third, 0.235 seconds behind than Aston Martin’s Fernando Alonso.

Verstappen and teammate Sergio Perez, who finished sixth, also complained about a lack of rear grip.

They trailed Lewis Hamilton’s Mercedes and Lando Norris’ McLaren, which received a significant aerodynamic improvement this weekend.

Even on the race-simulation runs later in the session, the Red Bulls failed to impress.

They were the fourth fastest car, with Alonso leading from Mercedes, Ferrari, and Red Bull.

How the practice sessions in Singapore went down on Friday
Russell on Hamilton, chasing Red Bull and finding tranquillity
Singapore Grand Prix preview on the Chequered Flag podcast
How to Watch the Singapore Grand Prix on BBC
Verstappen, the championship leader, said before the race that Singapore would be one of the places where Red Bull would struggle more than usual, and so far, his prediction has proven correct.

Verstappen’s rear ended up snapping at Turn 13, the exit of the Anderson Bridge, while Perez grumbled over the radio about feeling like he was going to crash on every turn entry.

“This track is going to be one of the toughest of the season for us,” team principal Christian Horner said between Friday sessions. The characteristics do not naturally play to the car’s strengths, and we will have to play at the top of our game to keep this winning streak going.

“High speed and combined [braking and turning corner] entries have been strong for us, whereas 90-degree corners have been more difficult for us.” But we can still come.”

Verstappen is on a record-breaking 10-race winning streak, and Red Bull has won every race this year.