LONDON Nov 9 Lewis Hamilton may have had some regrets already about his decision to join Mercedes next season, according to his McLaren Formula One team principal Martin Whitmarsh.
In an interview with the official Formula One website (www.formula1.com), the Briton also said Mexican Sergio Perez probably did not know what is about to hit him as Hamilton's replacement.
"I think he has on occasions, yes," said Whitmarsh when asked whether 2008 world champion Hamilton, who is replacing retiring seven-times champion Michael Schumacher at Mercedes, might have regretted his decision.
"Probably, when you make a decision you have to tell yourself that the decision is made so you have to look forward. You say okay, that it is in the past so you don't spend too much time thinking about why."
Mercedes have won one race, in China this year, since they took over the title-winning Brawn GP team at the end of 2009.
McLaren have won five grands prix this season alone and are the second most successful team in terms of wins in the history of the sport.
Whitmarsh said it would be an emotional farewell with Hamilton after the last race of the season in Brazil later this month and added that there had been some such moments already since the driver decided to leave.
"I hope he thinks today that he's made an awful mistake and I hope he thinks that next year. He's made that decision and he has to live with that decision," said the principal.
Perez is joining from Sauber, where he has had three podium finished this season but has also failed to score a point in the four races since his move was announced.
He will be joining 2009 world champion Jenson Button at McLaren and Whitmarsh expected the 22-year-old to learn everything he could from the older Briton.
"When Sergio gets to Australia (for the first race) in 2013 he will arrive with the kind of pressure that he can't imagine right now," said the team boss.
"At the first race, if he is not on the first two rows and fighting for a win the pressure will start to ramp. He doesn't know that yet."
Whitmarsh said Perez could expect to spend a lot less time in Mexico and a lot more in the simulator, working with engineers and on improving his fitness.
"He will turn up considerably fitter and stronger than he is today," he said of next season."
The team boss repeated his view, expressed at the weekend in Abu Dhabi, that while he expected Perez to get the job done he could not be sure of how good he might be.
"You come to McLaren and you've got the scrutiny and the pressure," he said. "And you either do well and survive, or he will struggle. You asked me if we are 100 percent sure that he's the right man for us - I can't be.
"He has not always been consistent and maybe he has been a bit wild sometimes, but he has sparkled. The really good guys, they always find an opportunity to be there and do it," added Whitmarsh.
"Natural talent got him to where he is now and now we really will turn him into a professional racing driver, properly prepared." (Reporting by Alan Baldwin, editing by John Mehaffey)