Mercedes team principal Toto Wolff has conceded the team is wary of 'game-changing' innovations from rivals this year.
F1 enters its new era with the opportunity for teams lower down the pecking order to gain ground on the heavyweights, with a complete reset of car design coupled with regulations that include a sliding scale of wind tunnel time depending on a championship position.
With the late finish to the last campaign, the sliding scale is set from 2020's standings, meaning there are five incremental steps between Mercedes' tunnel time and Ferrari's, despite the Scuderia finishing third last term.
With Mercedes in a season-long battle for the title with Red Bull, the Silver Arrows is theoretically on the back foot in development compared to teams that could afford to switch full focus to this season's car early on, with the wind tunnel restrictions further impacting upon the design team.
Asked where Mercedes' biggest threat was coming from, Wolff replied: "The ability of having more wind tunnel [time] is, of course, something you need to bear in mind.
"The advantage of finishing sixth versus first over the course of the season is a couple of tenths [of a second], and you need to catch up.
"We were part of these regulations. It's good to create competition so we shall see where everyone is.
"Personally, I'm not discounting any teams. Everyone could be high up in the standings at the beginning of the season. We saw it in 2009 with the double diffuser.
"If a team is innovative and discovered opportunities that could be game-changers, everyone can be ahead at the beginning."
Addressing the strain of fighting for the title last year when developing the W13, Wolff insisted "there weren't any major issues" but was adamant the team wouldn't rest on its laurels.
"From the beginning of the 2021 season we had a precise plan, a well-mapped out [plan] is probably the better word, as to how long we would continue the development of the W12 last year, no matter how the championship would pan out," he explained.
"We've followed that plan and our timeline, and it's all come together well for the moment.
"We fired up our car in December. That's the earliest we have ever done. That is no guarantee for success. We just need to keep on working and see if it performs as expected over the tests, in Barcelona and then Bahrain where there are more representative conditions.
"It's encouraging at the moment but there is nothing being taken for granted."