Mercedes boss Toto Wolff claims Red Bull are "in the favourites circle" for Formula 1 championship glory in 2021.

Last year, the German manufacturer dominated once again, winning 13 of 17 races as the secured a seventh consecutive Drivers' and Constructors' Championship.

However, it was Red Bull who ended the year with a commanding victory in Abu Dhabi, albeit against a handicapped Mercedes team, something team boss Christian Horner admits might have riled up the rivals.

"The question is how far below [their full potential] Mercedes were there [in Abu Dhabi] and what the effect was of having to cut performance because of reliability issues," he told Auto Motor und Sport.

"The win was good for us, but I'm afraid it has also helped to motivate Mercedes even more. But you still have to beat them [when you can] and we are racers from top to bottom in the team."

Certainly, Mercedes is anticipating a much tougher battle with Red Bull in 2021, who have an upgraded Honda engine and Sergio Perez now alongside Max Verstappen.

“That is a very strong combination,” Wolff told Austria's SpeedWeek.

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“Red Bull Racing actually had the fastest car at the end of last year, so the team is in the favourites’ circle in 2021, especially in the Constructors’ Championship, with drivers of this calibre.

“I see Red Bull Racing as a double challenge, so in both World Championships.”

However, Red Bull's outspoken advisor Helmut Marko didn't need long to respond.

“At the moment there is no driving, so you have to create tension with words,” he told F1-Insider.com.

“We hope to be among the front runners, but Mercedes is the clear favourite. They have won all the titles since the hybrid era in 2014.”

Earlier this week, Red Bull released two studio images of their 2021 car but then decided to keep their filming day secret, for now at least, at Silverstone on Wednesday.

But Horner had this to say about it after it was revealed.

"Last year we had problems with the aerodynamics, what we saw in the wind tunnel did not correspond to what we had expected," he explained.

“We’ve worked very hard to understand why we struggled for correlation. So we learned a lot during 2020, and of course the challenge now is to apply that in 2021.

"You know the engineers, if you allow them to change something, they do it. Probably every detail would then be optimised again but the rules have somewhat restricted this process," he noted.

"I think we will only know what sort of progress we’ve made once we get racing from Bahrain onwards."

With much of the car carried over due to the development restrictions, it also means Red Bull will skip a number on their chassis list.

"It's more honest to call the car RB16B," the team boss claimed. "The next model for 2022 will be RB18, which is why there will never be an RB17."