It quickly became clear at the start of the year that Mercedes would not have an easy ride to the title in 2021.
After seven years of facing no serious competition for either the drivers' or the constructors' title, the reigning world champions were suddenly on the back foot. Red Bull emerged as the team to beat in pre-season testing as Mercedes struggled to adapt its 2020 car to regulation changes aimed at slowing the entire field to protect Pirelli's tyres.
The rule changes clearly impacted Mercedes' design concept more than its rivals, but that came with the bonus of creating one of the most competitive seasons to date as Red Bull finally got its car and engine package right from the first race.