Red Bull have concerning McLaren theory as Lando Norris title bid hangs in the balance

believes that the 's decision to push into changing their 'mini-DRS' rear wing has impacted the team's speed off the back of a difficult weekend at the .

McLaren flickered between being the second and third fastest team at the Circuit of the Americas at the weekend with championship contender Lando Norris unable to finish higher than third between the sprint race and Grand Prix, despite claiming pole position on Saturday.

This had a disastrous effect on Norris' hopes of securing a maiden World Championship and he now trails rival Max Verstappen by 57 points with just five rounds of the season remaining.

According to Horner, the performance swing could have something to do with McLaren's rear wing. Footage emerged of the wing flexing under load in Azerbaijan a few of races ago, and after a brief probe, Andrea Stella's team were told to make changes.

"Small details do make a difference, and particularly when the cars have converged as they have," Horner explained in Austin. "It's all about marginal gains. That's what Formula One is all about. So yes, inevitably, there will be a difference from it. How material it is will vary from circuit to circuit."

This theory has been denied by McLaren chief Stella. "I would be surprised that there's only a couple of teams that had to make adaptations to the rear wing," he explained.

"Our rear wing was adjusted after Baku, following some of the conversations we have had, and with the FIA providing some references as to what they would like to see. But this is a really minor element in terms of car performance. It does not have to do with any performance switch from event to event.

"None of the performance that we see, being better, being worse, should be associated with this. And I think this is not only for McLaren, it's for any team, with the fact that some teams might have been asked to adjust the behaviour of the rear wing."

Norris isn't the only one who needs to worry about his World Championship chances. McLaren looked to have dropped Red Bull in the constructors' battle, but Ferrari's one-two finish without any upgrades to help has raised eyebrows, and Fred Vasseur's squad find themselves just 48 points behind with plenty of races in which to catch up.