Jenson Button could manage no better than ninth in the Australian Grand Prix after a weekend where McLaren admitted it was surprised by how far off the pace it was.
Its problems, allied to the fact that the 2012 car ended the year as the pace-setter, led to talk in Australia that the team could update last year's MP4-27.
However, following analysis by its engineers of where the 2013 car is lacking, McLaren is convinced that sticking to the current model is the best way forward.
Its stance has been sealed by the fact its data suggests the car is not lacking downforce, but its operating window is too 'peaky'.
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Team principal Martin Whitmarsh said: "At the moment we have to work hard on this car.
"We know it has got some areas of high potential and we know it has potentially more downforce than last year's car.
"We just need to understand it and make sure it [the performance] is accessible.
"We have all had cars in the past which have been difficult to get performance out of even though some of the [downforce] figures are quite impressive.
"This car seems to be difficult in that regard and we need to work on it, understand it and fix it."
Whitmarsh concedes that there is no quick fix for McLaren's problems, but he has no doubt the MP4-28 can be improved.
When asked if he was confident his engineers had a grip on what was needed to make the car better, Whitmarsh said: "I think coming out of a weekend like this and saying the engineers are confident would probably be a bit strong.
"But we believe in what we can do as a team. I am sure we are going to get there.
"It probably won't get there as quickly as I would like it to, but I will be encouraging them to do so."
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- Martin Whitmarsh