Red Bull team principal Christian Horner has conceded defending Max Verstappen's F1 world title will be "incredibly difficult" despite motivation within the team being "sky high".
Verstappen scored his maiden world drivers' crown after the controversial climax to last year's Abu Dhabi Grand Prix.
Although confident the team will once again feature at the sharp end of the grid, Horner reflected that the significant change in the technical regulations for the coming season has added an extra degree of 'difficulty' to the Dutchman's title defence.
"I think 2021 will go down in history as one of the all-time great years," said Horner, speaking at the launch of the RB18.
"I can't remember a year like that in Formula 1 where it was so close between two drivers from the very first race to the very last.
"Our challenge is now to build on, now that we have that number one on the car, is to keep it on the car and defend that title with Max which, with a brand new set of regulations, is going to be incredibly difficult.
"We've massive competition out there but motivation is sky high and we're riding on the crest of a wave from last year."
F1's biggest change in "30 to 40 years"
The aerodynamic changes introduced for the coming season have drastically changed the look of F1 cars with the boxy wings replaced with curved, less cluttered surfaces.
Asked if there was anything that could be taken from 2021 into the new year, Horner added: "You can always learn from previous experiences.
"You're always improving, but with a completely new set of regulations, it's going to be all about the development, how quickly the teams get on top of this new set of regulations.
"The biggest regulation change for 30 to 40 years in Formula 1, so development is going to thick and fast, and with the cost cap it's got to be efficient."