The pair worked together between 2002 and 2006, when the now 32-year-old won nine grands prix for McLaren.
Raikkonen switched to Ferrari in 2007, winning nine more races and the title, but after 2009 he quit formula one to go rallying and Nascar racing.
He has returned to F1 with Lotus this year, and despite not yet adding to his tally of career wins, the ‘Iceman’ is tipped as a dark horse for the 2012 championship.
When asked about Raikkonen, McLaren team boss Whitmarsh told Brazil’s Totalrace: “He is very talented.
“I think he is one of the fastest men on the planet,” he added.
“People tend to underestimate Kimi, because of how little he talks. But he is a very intelligent and impressive driver.
“The Lotus is a good car and so, put together, they’re a real threat,” said Whitmarsh.
“I’m sure you’ve noticed that Kimi does not make many mistakes; he always does a good job.
“So I’m not surprised and I think he has the ability to improve even more throughout the season,” he added.