In Austin, Sergio Perez took a step towards ending the speculation surrounding his future at Red Bull.

The Mexican has a firm contract in place for 2024, and team boss Christian Horner says there is "no such requirement" in that deal mandating that he hang onto second place in the drivers' standings.

But Perez at least eased some doubts about his performance slump during the US GP weekend by finishing fifth on Sunday - which became fourth after Lewis Hamilton's disqualification for an excessively worn floor.

"He (Perez) actually drove a decent race. He has made good progress," Horner said.

Tellingly, Dr Helmut Marko had even higher praise.

"Perez's race was flawless and his overall performance was good and satisfactory," he told German-language broadcasters.

"From ninth on the grid, he achieved the maximum possible. On the medium he drove the same laptimes as Max (Verstappen)," Marko continued. "A clear upward trend for Checo.

"We can now expect better performances from him in the future as well. Usually, drivers spend one day a week on the simulator, but on his own initiative he asked to spend three before coming here," the Austrian revealed.

"That shows that he is serious about getting back to being competitive again," Marko told Sky Deutschland.

As for the 33-year-old driver himself, Perez is optimistic about taking yet another step forward this weekend at home in Mexico.

"At times our speed was very good and at times we lacked it," Perez said. "But we know what we did wrong, so I am very optimistic for Mexico."

Verstappen, meanwhile, managed to move up from P6 on the grid to win the race, but the Dutchman actually complained about the handling of his Red Bull.

"We had changed the brake pads and somehow he didn't have the right feeling," Marko explained. "It was incredibly difficult for him to drive at the limit. But he managed it masterfully.

"It was definitely the toughest race this year."

What is also clear is that Mercedes' new floor - although revealed to be illegally worn after the race - proved a success, with Hamilton's team only ruing a bungled strategy that prevented a potential win.

Marko was impressed.

"Lewis drove a sensational race and didn't make any mistakes," he said.

Mercedes boss Toto Wolff agreed: "The positive side is that our upgrades work and the car was fast."

But he is concerned that it's not necessarily a sign that Mercedes is now rapidly catching up with Red Bull's dominance.

"In twelve years I have never felt optimistic," Wolff smiled. "They (Red Bull) probably stopped developing three months ago and are looking at next year.

"We've new brought a new upgrade and that's why it's shifted a bit. But the good thing is that the direction of development is right. We wanted to see if the new floor works."

Finally, Marko said Red Bull is not too worried that, given the way Verstappen was booed by the American crowd on Sunday, the situation could get even uglier this weekend in Mexico.

"Mexican people are very nice," he said. "Here, there were some fans who were perhaps a little more aggressive, but Max will be well guided in Mexico." body check tags ::