Guenther Steiner believes there are huge doubts surrounding Red Bull’s expected upgrade at this weekend’s United States Grand Prix as they look to close the gap to McLaren.

Christian Horner’s outfit have not won a race since the Spanish Grand Prix in June – a run stretching to eight races – and McLaren now lead the constructors’ standings by 41 points.

However, Max Verstappen leads the drivers’ standings by 52 points to Lando Norris in second, with six races and three sprint races remaining.

Yet former Haas team principal Steiner believes the four-week interlude since the last race in Singapore will have little effect, with Red Bull’s “magic floor” already long in the works.

“Everything is planned beforehand. I don’t think you have any advantage,” Steiner told the Red Flags podcast.

“What is coming for Austin is already prepared. A week or three weeks? I don’t think the preparation level is any different.

“The big question is: how big is this upgrade, this apparent ‘magic floor’ which is coming to Austin, to help them catch up to McLaren?

“That’s the big question. The rest is straightforward.”

Steiner believes catching the new frontrunners McLaren will be a step too far for Red Bull, but did emphasise the importance of Red Bull staying ahead of Ferrari in order for Verstappen to close out a fourth-straight title.

“I don’t think catching McLaren this year will be possible,” he added. “What they showed in Singapore was amazing”

“The Ferrari can play a bigger role than they played in Singapore in the world championship. In theory, they should be in front of Max. They didn’t qualify, then there was no red flag or Safety Car to help them. They had to fight which wasn’t easy.

“McLaren is in a good way but Max will fight until the end to hang onto the world championship.”

F1 returns with the fourth sprint weekend of the season with the United States Grand Prix (18-20 October) in Austin.