Sergio Perez’s calamitous weekend on home soil has been magnified even further after one of his biggest backers announced their company will be parting ways with Red Bull Racing.

The pressure is firmly on Christian Horner and Red Bull with Perez seemingly on life support, opening the door for Daniel Ricciardo to fill a vacant seat in one of the RBR teams to see out the season.

Telmex, the Mexican telco owned by one of the world’s richest people, Carlos Slim, is set to part ways with Red Bull as American corporate giant AT&T announced they will be taking pride of place on the team’s livery next season.

Slim, who is reported to be worth a staggering $140 billion, is a long-time backer of Perez but has had to publicly qualify his support for the embattled driver after it was announced that the Slim-affiliated sponsor - Telmex - will no longer be on the Red Bull cars in 2025.

Just days ago, Red Bull announced the expansion of its partnership with American telco giant AT+T - a direct competitor of Telmex’s, particularly in Mexico with Mr Slim admitting Red Bull’s Telmex deal could soon be axed.

“We are still talking to them, but the intention will always be to continue to support Checo. We will continue to support him without a doubt,” Slim said.

“Checo’s contract is separate from our sponsorship contribution to the team.

“It has always been like that since we have been with this team. But if we no longer have the opportunity to work with the team, we will definitely want to continue with Checo.

“The intention is to continue that collaboration, regardless of which team Checo is with.

Christian Horner’s post-race interviews around Perez’s disastrous Mexico weekend paint a dire picture for the Red Rull star and coupled with the departure of Telmex, every indication is now that RBR will be looking to replace the 34-year-old Mexican with a new driver in the top flight team soon.

“We are now only third in the constructors’ championship,” Horner said.

“As a team, we have done everything we can to support Checo, But there comes a point when we can’t do any more.

“That is the point at which difficult decisions have to be made.”

With four rounds left in the F1 season and world titles and constructor’s championship standings on the line, it is yet to be seen if Horner and RBR will allow Perez to see out the season or potentially move another driver in to replace him.

Liam Lawson has had a baptism of fire with RBR since replacing Daniel Ricciardo and has been spruiked as a potential top-tier replacement, albeit a very inexperienced one.

Ricciardo, left RBR after the Singapore GP with team bosses almost apologetic about the circumstances, potentially leaving the door open for a stop-gap return for the Aussie to assist Max Verstappen in the chase for the world title.

Meanwhile, McLaren has told Lando Norris he has no need to change the way he drives in the Formula One title battle with Red Bull’s Max Verstappen, according to team boss Andrea Stella.

The Briton, often his own harshest critic, had told reporters before Sunday’s Mexico City Grand Prix that he needed to make changes to fight at the same level as his championship-leading rival.

Stella said after Norris finished second in Mexico, with Verstappen sixth and twice punished for track incidents with the McLaren driver, that Norris should keep doing what he did.

“Our conversation and our internal reviews have always been very clear,” the Italian told reporters.

“’ Lando -- we like, we approve, we confirm the way you go racing. It’s not for you to go there and try to find justice yourself’,” he said.

“’ You go racing in a fair, sportive way like you do and then there needs to be a third party, that is the stewarding, that will say whether some manoeuvres are correct or not. Don’t be desperate, (you) don’t have to prove anything.

“’ You go racing fair and square’. This is what we want from Lando, this is what Lando wants from himself.”

Norris is 47 points behind Verstappen, still the clear favourite for a fourth successive title given the substantial gap with four rounds remaining.

Stella saw positives on Sunday despite rivals Ferrari taking another big step in the constructors’ championship with Carlos Sainz winning and Charles Leclerc third.

The Italians are now just 29 points behind leaders McLaren in the standings.

“When I look at the incidents in the early laps of the race, there’s a little bit of disappointment because without that couple of incidents, I think Lando could have fought for the victory,” Stella told reporters.

“Anyhow, this is just if, if, if. For me the important fact is that we have seen that the car is competitive, the upgraded car seems to be now on par with Ferrari at a track that we thought would be more in favour of Ferrari.

“So this is encouraging for the remainder of the season.”

with AAP.