Red Bull’s drivers will start no higher than 11th and 13th for Sunday’s grand prix, though Verstappen’s weekend could get even worse with the reigning world champion facing a triple investigation for separate impeding incidents.
Red Bull’s unexpected lack of competitiveness threatens to bring Verstappen and the team’s remarkable winning streak to an end.
"It's very very confusing to have dropped the amount of pace we have. The car is not responding to changes - understeer, oversteer, braking issues,” Horner told Sky.
"It's like we haven't managed to get the tyre into the right working window. Usually when you see a gap that big, it's because the tyre isn't fundamentally working.
"We have tried different things with setup, different preparations and it's just not happened.
"A lot for us to understand tonight to try and turnaround and it will be very, very tough for us to make good progress tomorrow but we will be trying very hard.”
Horner added: “The car that we have here for qualifying is essentially the identical car that we had two weeks ago in Monza and a week before that in Zandvoort.”
Asked whether the technical directive introduced to clamp down on flexi-wings had an impact on Red Bull’s performance, Horner replied: “No. Nothing’s changed on the car.
“We tried a new aero part on Friday. We thought ‘ok we’ll revert on that component’.
“It’s a tried and tested set-up that we have but it just hasn’t responded on this circuit, on this asphalt. Trying to get the tyres into the window has been very, very hard for both drivers.
“We’ll see tomorrow. We won’t give up on anything but starting outside the top-10, on a track that’s really hard to overtake at, we’ve got quite a lot on.”