Given the depths of McLaren's problems, it triggered rumours McLaren could simply revert to its 2012 car, which could be easily converted to the similar new rules by tweaking the design for tougher wing load and impact crash tests.
Team boss Whitmarsh fuelled the speculation early this week by saying "Purely from a technical point of view, it would be possible".
But he is now quoted by the BBC: "All our efforts are currently focused on understanding this year's car, not considering last year's car.
"At the moment we have to work hard on this car," the Briton added.
"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 (the performance) is accessible."