Lewis Hamilton says Mercedes "still have a lot of work to do" ahead of the season-opening Bahrain Grand Prix as testing ended at the Sakhir circuit with world champion Max Verstappen on top.
"I am sure everyone can figure that out, we are not the quickest at the moment.
"I think Ferrari look to be the quickest and perhaps Red Bull and then maybe us or McLaren," the seven-time world champion said on Saturday.
Verstappen, who denied Hamilton the world title on the last lap of the last race in December, posted a 1min 31.720sec to finish the final testing day of three atop the timesheets.
Mick Schumacher was allowed out later than the rest of the grid to compensate Haas who missed Thursday's morning session due to freight delays, and in more favourable cooler temperatures the German posted the second quickest time.
Then came the Ferrari of Carlos Sainz, 0.695s behind. Fernando Alonso for Alpine was next ahead of new Mercedes driver George Russell with Hamilton a distant 17th, over four seconds adrift.
Mercedes unveiled a radical interpretation of the new technical regulations designed to promote closer racing with their 'no sidepod' car which they are counting on to power Hamilton to an unprecedented eighth world championship.
But the Briton says from what he is told "we have considerable amount of pace to find".
"Obviously it's a little bit too early to have that kind of thoughts but at the moment I don't think we'll be competing for wins," he forecast.
With pre-season testing performances notoriously difficult to read Mercedes' grid rivals will take his cautious prognosis with a pinch of salt, if history is anything to go by.
Last year Red Bull ruled pre-season tests in Barcelona only for Hamilton to emerge the winner in Bahrain.
"People keep talking about whether we are talking ourselves down or not, but it's a bit different this year," he observed.
"Obviously next week, we'll get a much better showing of our pace but… I think people will be surprised, maybe?
"There is potential within our car to get us there, we've just got to learn how to extract it and fix some of the problems, which is what we are working on."
Alpha Tauri's Pierre Gasly got a close up view of Hamilton with the French driver reporting: "I could see Lewis was struggling as well and I think they do have some work to be fighting right at the top."
Verstappen produced the quickest time of the three days following a 360 degree spin.
Second-best Leclerc was feeling in a good place ahead of the first race of the season in Bahrain on Sunday week.
"It's definitely one of the smoothest preparations I've had for a season," said the man from Monaco.