Martin Whitmarsh concedes McLaren have cause for concern after neither driver made it into the top ten in Friday's practice in Melbourne.
McLaren had a difficult time in pre-season testing and it was more of the same in Friday's first practice for this season.
Jenson Button finished outside the top ten, 2.386s off the pace, while his new team-mate Sergio Perez was a further three-tenths adrift.
"I think we should be worried about the pace," Whitmarsh told Sky Sports F1.
"It is a tough day in the office for everyone at the moment, we are lacking grip and there is a lot of head scratching at the moment, but certainly we are lacking pace.
"I think we are still learning and there is a lot we still need to learn about this car. But we have struggled frankly to quite understand how it is performing - understanding the tyres and the car.
"We took the decision to make a lot of changes and knew that to some extent that would put us back a little bit, but we were hoping to get on top of that before the first race.
"As of today we are still undoubtedly struggling and that is something we need to gather good information on and work through it this weekend."
And Whitmarsh is not the only member of McLaren who has concerns, however, sporting director Sam Michael is reversing judgement until after Saturday's qualifying.
"Definitely, we're not where we need to be at this point in time," Michael said.
"We made quite a few changes to the car over the winter and we still believe they'll go good for the course of the season.
"We don't know to be honest, until we go through a race weekend. In practice, we've not done much more than what we've done in testing. You don't have knowledge of what people have done until you've gone through an official session (qualifying and the race).
"Whenever you change something that's very well optimised, it is a bit more difficult to get it right straightaway. That happened to Ferrari last winter, to some extent, but by the fourth or fifth race they were there.
"I think most of the understanding of where we need to improve is there. I think a lot of the differences to last year's car we understand pretty well, but to achieve what we need to achieve... we're still working away on that."
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