Lewis Hamilton has warned Mercedes face "much bigger problems" than when the team was able to fight back from a slow start in testing last year.
The Silver Arrows struggled with technical changes in 2021 but managed to pull it back to take victory a year ago in the season-opening Bahrain Grand Prix.
But with issues in adapting to F1's new regulations, Mercedes appear to be struggling to remain on terms with Red Bull and Ferrari in testing, a fear confirmed when the cars officially kicked off the new campaign during practice in Bahrain.
The best Hamilton could muster was ninth on the timesheet, over a second down on F1 champion Max Verstappen, with his W13 plagued with issues as a result of aggressive porpoising.
Asked if the team could perform a turnaround similar to last year, the seven-time champion explained: "We had small problems in the car [last year], relatively, compared to this year. We had smaller problems.
"We are faced with much much bigger problems this year and everything we do to try and fix it doesn't really change that.
"It appears it is going to be a longer-term fix so nothing in the short-term."
New team-mate George Russell finished the day fourth fastest and asked how their set-ups differed through the day, Hamilton replied: "I don't know, I haven't been looking at George's car.
"We were trialling different things but I have not been following what he has been doing. I focus on the problems I have on my side."