Max Verstappen is the driver Lewis Hamilton "fears the most", says Red Bull team boss Christian Horner.
Horner believes the Dutchman, 21, is ready to take the fight to Hamilton and Ferrari's Sebastian Vettel in a title battle, should his Red Bull team prove competitive in 2019.
Verstappen finished fourth in the drivers' championship in 2019.
"He has all the skills to take on Lewis or Sebastian or whoever it is," said Horner.
"I don't think he lacks anything to take those guys on and he's probably the driver they fear the most."
Verstappen, who had an error-strewn start to last season, eventually won two races - in Austria and Mexico - and finished only two points behind third-placed Kimi Raikkonen.
Horner says he has grown in the past year and is "in a better place to deal with the challenges he faces".
He added: "Max has evolved so much. He is more worldly, more experienced. He is very quick and very determined and has his own character. He is now in a very rounded position. He has absolute determination and zero fear."
Hamilton is aiming for a sixth world championship this season to move just one short of Michael Schumacher's all-time record but Horner said it was inevitable that his ability would sooner or later begin to decline.
"Lewis is at a different stage of his career," Horner said. "He has all that experience but he is 34 and at some point it is only natural that the brightness of that talent will start to fade.
"Can he have that speed all the time? It's just human. In 10 years, it will be the same for Max."
Verstappen has a new team-mate at Red Bull this season following Daniel Ricciardo's move to Renault.
Horner said Frenchman Pierre Gasly, who is entering only his second season in F1, was "very quick" but that Verstappen's greater experience means "the team will be looking to him to lead the development".
He said Verstappen had learned from his mistakes and that the 'community service' charge he served for starting an altercation with Force India's Esteban Ocon following their crash in Brazil last year had opened his eyes.
The 21-year-old was forced by governing body the FIA to attend a race of the all-electric Formula E series and observe the stewards.
Horner said: "It was interesting talking to him after the Formula E race. Not that he was particularly impressed by Formula E, but he came way from being with the stewards and said: 'Crikey, these guys have got difficult decisions to make in terms of do they impose a penalty or do they not.'"
Red Bull will reveal their 2019 challenger on 13 February
Red Bull are starting their first season with new engine partner Honda after ending an often-fractious relationship with Renault, and Horner said he expects them to move forward from last year, when they won four races but were usually "in the void between Mercedes and Ferrari and the rest".
"Progress is our target," he said. "The objective is to be more consistent across all circuits and hopefully with more horsepower than last year, that will only help to reduce that gap."
He said Honda had "had a strong winter" and were "making good progress" but "it will all depend on what the others have done".
Red Bull have for the past five years had a power deficit to the best engines.
Horner said Red Bull accepted that they may have to take some grid penalties for using more than the permitted number of engine parts this season.
"It's a huge challenge to do the season on three engines," he said. "We'd rather take a penalty if it means consistent progress. We're extremely hopeful the performance will be a step from where we've been the last few years."
Leclerc has already experienced life in his new Ferrari during end of season testing in Abu Dhabi
Horner said it would be "very interesting" to see how Charles Leclerc gets on in his first season at Ferrari, following his promotion from Sauber.
"Charles is a really exciting talent. Sebastian [Vettel] is 31. He has a youngster coming in and starting to put pressure on.
"Seb had Kimi [Raikkonen] pretty easily covered and may have to work harder. But he could find another level. It could be good for him."
Ferrari enter the season with a new team boss following the replacement of Maurizio Arrivabene with Mattia Binotto, who moves up from technical director.
Horner said: "It's a big job for Mattia because you can't do both roles, you are either a team principal or a technical director. He's probably running between two offices at the moment."
And he said Mercedes could stumble under pressure if their dominance was not as great as in the past.
"With a team like that, how they deal with pressure of not winning consistently, it will be interesting to see how they handle that in terms of expectations management," he said.
F1's bosses have changed the technical rules this year to force teams to run a new front wing design that they hope will make the racing better, by making it easier for drivers to follow another car.
But Horner said he believed it would make no difference to the on-track action, although he said it might lead to some variability early in the season because "some people will have got it right and some people will not".
He claimed that F1 owners Liberty Media "would probably accept it was a mistake" to think they could "just take off a front wing and say it will make racing better".
Horner described this as "quite a naive approach".
He said Liberty had made some positive changes to the sport in terms of its promotion but added: "The more concerning thing is what is their blueprint for regulations and financially for what they want F1 to be from 2021 onwards."
He said he believed Liberty had "absolutely" underestimated the task of running F1 and he raised concerns about their methods for reducing costs by introducing a budget cap.
"It's vitally important any restructure is done on a fair and equitable basis. Financial regulations and governance are an enormously hard thing to police fairly and we are waiting to see how they do that."