After a poor weekend for the young Mexican in China, including a rebuke from Kimi Raikkonen following an on-track run-in, British commentator Martin Brundle said he would have signed Nico Hulkenberg for 2013 "ten times before (signing) Perez."
Immediately after Shanghai, Whitmarsh backed Perez's defensive driving in China, having told the 23-year-old to put his "elbows" out and "be robust without being dirty".
But he does admit that the Carlos Slim-linked Mexican needs to up his game.
"I know Sergio is not satisfied with his performance at the weekend, nor should he be," Whitmarsh told reporters.
The Woking based team's chief admitted Jenson Button's "fantastic job" in the sister car has made life difficult for Perez.
"A lot of credit to Jenson, but we as a team have to step up and support a young driver who has an enormous amount of talent," said Whitmarsh.
"With these sorts of tyres, which are very fragile, with the balance not quite there, with tricky racing, he did a reasonable job.
"As a young guy in a big team with lots of expectations you are under a lot more scrutiny, and it's tougher when you've a teammate doing a great job, so there is pressure there," he added.