Mercedes threw down the gauntlet to their rivals two weeks out from the start of the Formula One season as Lewis Hamilton posted a blistering lap on the penultimate day of testing in Barcelona.
Hamilton, who for much of the winter has played down the German manufacturer's hopes following his move from McLaren, set the best time so far from two pre-season tests at the Circuit de Catalunya, his lap of one minute 20.558 seconds some seven-tenths clear of Ferrari's Felipe Massa.
With just one day of testing to go before the season kicks off with the Australian Grand Prix on 17 March, Mercedes' pace will have many reassessing the likely look of the Melbourne grid.
No one at Mercedes will get carried away, especially as times from pre-season testing are hard to interpret with teams running so many differing set-ups, yet their rivals will inevitably sit up and take notice of the W04's potential after today's showing.
"There's still a lot of work ahead of us to get to where we want to be but the team is doing a great job," said Hamilton, who will hand over driving duties to team-mate Nico Rosberg for tomorrow's final day.
"The reliability, the mileage and the step-by-step improvements that we have achieved during the three tests are all very encouraging.
"Whilst we've been focusing on our own performance, we definitely haven't seen the full potential of our competitors yet, so it's difficult to predict where we might be."
Hamilton set his time in today's morning session, during which Mercedes focused on short runs using the softer - and quicker - Pirelli tyre.
Ferrari driver Massa waited until the afternoon to do a few shorter runs but his best time, although good enough for second place, was nearly a full second down on Hamilton's.
The Brazilian was forced to stop the F138 with less than half an hour remaining due to a problem with the left-front suspension, but it did not prevent the team completing their planned programme.
Adrian Sutil completed a race distance on his way to a strong third for Force India, for whom Britain's Paul Di Resta will take over driving duties tomorrow, while Pastor Maldonado was fourth, one tenth of a second up on team-mate Valtteri Bottas, as the Williams duo shared the new FW35.
Esteban Gutierrez of Sauber took sixth place ahead of Red Bull's Mark Webber, who managed just 59 laps today, most of which were spent running on hard tyres and concentrating on long runs.
McLaren's Sergio Perez was eighth ahead of Jean-Eric Vergne's Toro Rosso and Lotus pair Romain Grosjean and Davide Valsecchi.
Marussia new boy Jules Bianchi completed 74 laps on his first outing since being confirmed yesterday as the replacement for Luiz Razia, whose hopes of driving for the team in 2013 were dashed due to reported sponsorship problems.
Giedo Van Der Garde completed the most laps of any driver today - 126 - but that could not prevent the Caterham rookie bringing up the rear, nearly four seconds shy of Hamilton's time.