Whitmarsh, team boss, might ultimately shoulder the blame, Scot Coulthard wrote in a column for the Telegraph.
"You cannot escape the fact that there is pressure upon Martin Whitmarsh as team principal, for in the end, the captain of the ship is responsible for its navigation," said the 41-year-old, who drove for McLaren between 1996 and 2004.
"F1 is not a sport where people shy away from responsibility. Any evidence of a lack of commitment, lack of focus, or an inability to deliver consistently, is immediately addressed.
"Failure is not an option," Coulthard added.
There has been talk of McLaren scrapping the MP4-28 in favour of reverting to the winning 2012 car, but that cannot be done in the very short term.
"Am I excited for the next race (in Malaysia)? We certainly will not be quick," Jenson Button is quoted by Brazil's Totalrace.
On the possibility of the 2012 car returning to action later on, Whitmarsh is quoted by Italy's Autosprint: "Purely from a technical points of view, it would be possible."
As the pressure ramps up, Button backed his boss.
"Everyone looks up to Martin," he is quoted by the Daily Mail. "It's difficult to always be strong, but he is doing a bloody good job. There is no finger-pointing.
"We want to improve, but it is going to be a long journey for us I think."