McLaren will arrive at the Formula 1 season-opening Australian Grand Prix with a "number of unknowns" after failing to complete its testing programme, says racing director Eric Boullier.
After suffering one of the worst seasons in its history in 2015, McLaren appeared to begin this year on a better foot in pre-season testing.
It managed 780 laps in eight days at Barcelona this year, compared to just 380 across 12 test days last term.
But Boullier said: "We didn't manage to complete our final configuration and set-up work for the first race, so we go to Melbourne with a number of unknowns.
"It won't be an easy start to the weekend in that sense, since we'll need to concentrate on setting the car up for each session and readying the final specification of our package as soon as we get to Albert Park.
"Since the final pre-season test, there's been a huge effort back in Woking to bring new parts to Australia and it'll be good to finally get to the track on Friday and see how we fare.
"We are certainly a step ahead of where we were this time last year in terms of preparation.
"We have much more mileage under our belts and we've performed most of the necessary system checks that we were still working on during race weekends in 2015."
McLaren has steered clear of making public its expectations for this season.
Jenson Button says the team is just focusing on its own performance and he feels the new rules, such as the tweaked qualifying format and tyre regulations, should make the opening race exciting.
"We've been concentrating heavily on our own development and processes, so I'm looking forward to seeing where we are on a level playing field," he said.
"We're working hard behind the scenes to develop the car and bring new updates at every possible opportunity.
"Melbourne will certainly be a challenge, but our package definitely feels like a step forward from last year.
"There are so many more variables this year - new qualifying format, new tyre regulations, and Australia usually produces unpredictable races, so anything could happen."