Lewis Hamilton has poured cold water on Daniel Ricciardo's hopes of moving to Mercedes next year.
Ricciardo's value has never been higher after he delivered the most dominant weekend of his grand prix career in Monaco.
The Australian topped every practice and qualifying session in Monte Carlo before nursing his wounded Red Bull over the line for his second victory of the campaign.
Ricciardo, whose Red Bull contract is up for renewal, moved ahead of Mercedes' Valtteri Bottas in the standings and to within 38 points of Hamilton.
The 28-year-old has spoken of his desire to team up with Hamilton, while he can also count Mercedes boss Toto Wolff among his admirers.
Bottas and Ferrari's Kimi Raikkonen, 38, could yet be moved on at the end of the season, but Hamilton believes Ricciardo might have to extend his stay at Red Bull.
"I would imagine his future is at Red Bull," Hamilton said. "He is one of the top drivers so I am sure there will be options for him, and it is only Ferrari and Mercedes among the top teams that he could consider.
"But currently here at this team that is unlikely and I don't think that [Ricciardo joining Mercedes] is going to happen.
"I imagine at Ferrari that Kimi will want to continue, too. He is driving really well this year and doesn't seem to be ageing so I think he will go on a bit longer."
Red Bull vowed to build their team around Max Verstappen after tying him to a long-term contract, estimated to be worth as much as £20million-a-year, at the end of last season.
But Ricciardo's form, coupled with the 20-year-old Verstappen's error-prone campaign, has seen him emerge as the team's number one contender.
Ricciardo is currently earning significantly less than Verstappen on £12million-a-season but would surely demand as much, if not more than his under-performing team-mate to stay with Red Bull.
"At the moment, Daniel is the lead driver in that team," Hamilton added.
"I said to him that he is doing a solid, solid job. He has got a team-mate, from what I hear, making a lot more money than him, yet Daniel is more consistent in keeping the car together and more often than not pulling through.
"It is important to feel valued. He has got to keep his head down and keep dong what he is doing."
Hamilton, who himself remains in negotiations with Mercedes over his new deal, added: "He should definitely have a contract on the table but I was talking to him and I don't know if he has his options planned out. I was like 'get them to your manager, dude, and let me know if you want me to do it'."
Hamilton, Vettel and Ricciardo have all won two races each this year and the Brit, who holds a 14-point championship lead, added: "It is definitely is a three-way fight for the title.
"Ferrari still are the strongest. They have dropped the ball a few times and we have capitalised on that but Red Bull will continue to get stronger.
"It's challenging me more than I can express but I am loving that I have to dig deep."