Red Bull team principal Christian Horner was left confused by his drivers' lack of pace in qualifying for the Singapore Grand Prix on Saturday.

Championship leader Max Verstappen qualified 11th while team-mate Sergio Perez was even further down the pecking order and will be starting the race from 13th.

It is unfamiliar territory for Red Bull, who have won every single race this season and could wrap up the Constructors' Championship this weekend.

Horner said: "It's very, very confusing to have dropped the amount of pace we had. The car is not responding to changes.

"It's understeer, oversteer, braking issues, it's like we haven't managed to get the tyre in the right working window.

"Usually when you see a gap that big, it's because the tyre is not fundamentally working. 

"We have tried different things with set-up and different preparations and it's just not happened."

The reigning champions brought two new upgrades to Singapore but are struggling to adapt in what looks set to be a miserable weekend for the whole team.

Verstappen's qualifying time was over a second slower than pole-sitter Carlos Sainz, who secured top spot again after claiming pole in Monza.

Horner added: "Nothing has changed on the car. We tried a new aero part on Friday [a revised floor] and thought we would revert on it.

"It's a tried and tested set-up and it just hasn't responded on this circuit, on this asphalt. 

"Trying to get the tyre in the window has been very hard for both drivers. 

"Starting outside the top 10, at a track that's really hard to overtake at, we have quite a lot on."