Lewis Hamilton said on Wedneday that neither he nor Jenson Button has a chance of repeating their previous world title successes unless McLaren make vast improvements to their car.
The 26-year-old conceded, though, that the ongoing work of the McLaren engineering team meant that the car could become capable of challenging last year's supremacy of Red Bull.
"Do I believe I have a car to win the world championship at the moment? I don't, no," was his blunt assessment when he spoke to Autosport.
"But that doesn't mean it won't become a world championship-winning car.
"From today, the improvements we've had, it's something that can grow to be better, so as long as we keep pushing in the right direction with the development, and the new things we have coming several races down the line, hopefully they will enable us to close the gap and compete for wins.
"As long as we pick up a good few points in the first few races, then we won't be miles behind."
Hamilton, the 2008 world champion, finished fourth in last year's world championship.
He said it was vital that McLaren secured top-five finishes, at least, in the first four races of the season.
"Say for example we were able to be in the top five for the first three or four races, get those points, and then if we happen to have a car capable of winning, then it would still be possible," said the Briton.
"So I'm definitely not shutting the year off. Everything is still to play for."
However, the 14-time Grand Prix-winner said that Wednesday's testing session here had only shown McLaren how much progress they still have to make.
Hamilton recorded the fourth fastest time of the session, 1min 22.888sec, with German world champion Sebastian Vettel fastest in the Red Bull in 1:21.865.
"It has been a tough day in the sense that we've not done enough miles," said Hamilton. "I came here hoping to do more laps, to get in a good 100-odd laps, to get in a race distance.
"Usually at this time of the year, this is when we come with pitstops and one or two race distances a day, but we were nowhere near even completing one."