Max Verstappen has cast further doubt over whether Sergio Perez will remain at Red Bull next season.
Perez's seat with the world champions is in the spotlight following his poor run of form and his first-corner exit at his home race in Mexico last weekend.
Daniel Ricciardo, who out-performed his modest AlphaTauri machinery to claim the team's best result of the season by taking the chequered flag in seventh at the Autodromo Hermanos Rodriguez, is the man primed to replace the stuttering 33-year-old.
And speaking ahead of this weekend's Brazilian Grand Prix, triple world champion Verstappen suggested both men are in the running for the drive.
"I always had a great relationship with Daniel, and I have a great relationship with Sergio," he said.
"It is not up to me to make these decisions. But if it is Sergio next year, then great, because I have a great personal and working relationship with him, but if is Daniel, then we will also get along fine, too, and have a great time.
"Formula One can be a tough sport, but maybe also nothing happens. We will see."
Although Horner said it is Red Bull's "intention" to honour Perez's contract for 2024, he refused to confirm the Mexican would remain with the world champions beyond this term.
Ricciardo has a deal to continue with Red Bull's junior team AlphaTauri next year, but it is possible that the two drivers could trade seats in 2024.
"I have not (spoken to Red Bull about next season)," said Ricciardo, who won seven races across a five-season spell with Red Bull.
"All of the stuff round my contract next year has been related to AlphaTauri, and honestly, I would say that is as far as that goes.
"But having a weekend like Mexico was good for the soul. It was nice to have a weekend like that, but just to have one is not enough.
"This year was about me rebuilding and finding the old form, and the old me, and Mexico felt like that, but I have to stay grounded."
"There are always going to be some rumours in Formula One, we should not believe maybe the people that are saying those rumours." - Fernando Alonso
Meanwhile, Aston Martin's Fernando Alonso warned of unspecified "consequences" after the Formula One rumour mill went into overdrive with speculation about the double world champion's future.
The 42-year-old Spaniard was also linked with a shock move to Red Bull as a replacement for Perez, in social media speculation, after last Sunday's Mexican Grand Prix.
Some suggested he might be losing faith in Aston Martin, a team he joined at the end of last season from Renault-owned Alpine, with the Spaniard's loyalty also seemingly in question.
"I'm not demotivated at all, I'm still enjoying a lot the project, I love the team, I think we had an incredible season even if now we are not obviously fast enough," Alonso said.
"There are always going to be some rumours in Formula One, we should not believe maybe the people that are saying those rumours.
"These rumours are coming from people that are just social media guys, they want just some followers. It's a shame and I will make sure there are consequences."
The driver did not offer any further explanation on what the "consequences" might be.
Alonso started the season with three straight podiums and six top-three finishes in the first eight races, but Aston Martin's form has tailed off and he has not finished higher than sixth in the last six races.
Aston Martin have dropped from second place early on to fifth in the constructors' standings, although they have scored more than four times as many points as last season when they finished seventh.
Alonso has a contract to the end of 2024 with his team.
