McLaren boss Martin Whitmarsh says signing Sergio Perez is a risk

Hamilton decided to end his relationship with the Woking-based team, for which he has spent his entire Formula 1 career, to join rival team Mercedes from next year.

The 2008 world champion will be replaced by Mexican Perez, who made his grand prix debut with Sauber at the start of last season after finishing runner-up to Pastor Maldonado in the 2010 GP2 Series.

Perez has had a season full of up and downs this year, having finished on the podium three times but failing to score a point since he was announced as a future McLaren driver.

Whitmarsh concedes the Mexican, who will partner Jenson Button at McLaren, is still an unknown quantity for the team.

"He is a 22-year old. He is the same age now as when Lewis started. I think he has a lot of talent," said Whitmarsh.

"But I have to be honest and I don't know [about his potential]. We wouldn't have signed him unless we thought he could go to another level, but I think what I said is that we don't know.

"He has never experienced the type of pressure that these two guys [Hamilton and Jenson Button] are under. You turn up in a McLaren and if you are not on the front couple of rows then there is a lot of pressure applied to you.

"These two guys know it, they have experienced it, they live with it, and they thrive with it and do well.

"There are examples of drivers who can live with that pressure and other drivers who cannot, so I think it would be foolish of me to sit here and say, taking a very young driver, there is not an element of risk in it.

"But we would not have done it unless there was a possibility. Time will tell."

Perez has also been involved in several accidents in the last few races, including the Abu Dhabi GP, but Whitmarsh insisted that is not a concern for his team.

"I think a lot of people had incidents in that race and it was pretty incident-filled," he said.