Mercedes duo Lewis Hamilton and Toto Wolff admitted they had not anticipated Charles Leclerc to claim a stunning pole position for Ferrari in Singapore.
The slower Marina Bay Street Circuit was not expected to suit the speed of the Scuderia car this week, yet Leclerc blew Hamilton away with a blistering lap time of one minute and 36.217 seconds.
Hamilton, the reigning champion and season leader, now has work to do to deny breakout star Leclerc a third consecutive victory, having recorded poles in the past two races, too.
The shell-shocked Briton said: "I don't know where Ferrari picked up their pace because this is not known to be one of their tracks, but they did a great job.
"Charles really put some great laps in and I needed something special at the end, so I gave it absolutely everything I had.
"It was very, very close – I'm sure I nearly hit the wall a couple of times – but it was as much as I could get out of the car."
Hamilton is looking forward to Sunday's race, though, adding: "I'm really, really happy to be on the front row in the mix with them [Ferrari] and try to divide them tomorrow. We can be aggressive."
Team boss Wolff acknowledged he had also foreseen a challenge from Red Bull but not from Leclerc and Sebastian Vettel, who qualified third fastest.
Mercedes need a victory in Singapore to avoid equalling their worst run without a victory in the hybrid era thanks to Leclerc's sudden recent dominance.
"This is a circuit we thought the Red Bulls and Mercedes would battle for pole," Wolff told Sky Sports. "Ferrari's car is fast, they did a good job and we have to get our act together on Sunday.
"They are gaining a few tenths [of a second] on the straights but also very quick on the corners - quick everywhere.
"The statistics are against us, but the race has not started. If Lewis is able to get a good start and Valtteri [Bottas] can get up a position, then we're in a good position."
Red Bull star Max Verstappen was understandably disappointed after recording good times in practice but coming in fourth best on Saturday.
"The car felt alright but there was just not enough grip and I wanted to go faster," he said. "The four wheels were sliding.
"I'm a little bit surprised. After a positive Monza, we would expect to be really strong here and we weren't. We are too slow."