McLaren team boss Martin Whitmarsh believes that Lewis Hamilton has had moments of regret about moving to Mercedes for 2013 since the deal was announced.
The 2008 world champion's future was resolved in the week following the Singapore Grand Prix, when it was announced that he will replace Michael Schumacher alongside Nico Rosberg at Mercedes.
Hamilton has already played down his hopes for next season, and he has spoken of his desire to turn Mercedes into a top team as being one of the prime reasons behind his move.
But his current boss Whitmarsh, speaking to formula1.com, believes that Hamilton will have had some doubts about the switch since it was confirmed.
When asked if Hamilton has regretted his decision, Whitmarsh said: "I think he has on occasions, yes.
"Probably, when you make a decision you have to tell yourself that the decision is made so you have to look forward."
He added that it was only natural for Hamilton to highlight the positives behind switching to a team further down the grid than McLaren.
"You have to justify your decision," he said. "He's not going to say 'hey, they offered me more money'. He's also not going to say that he's made an awful mistake.
"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."
Whitmarsh also said that he still doesn't know why Hamilton left, and that he feels that the Briton was wrong to make his decision in the wake of his disappointing retirement from the Singapore Grand Prix.
"The simple answer is that I don't know," he said when asked what the reasons were for Hamilton's move.
"If I were speculating there are a number of factors and the prime one, I think, is that there comes a time when a man feels he has to flee the nest.
"He has been with us for so many years that I do not fully understand it.
"He told me right after Singapore and I am pretty sure he hadn't made his mind up until the Monday or Tuesday after Singapore.
"It is always bad to make a decision in the aftermath of a bad race.
"I respect his decision, but I believe that he would be better off with us - we are the stronger team - and we intend to beat him next year."
F1 editor Edd Straw
If Lewis Hamilton did have any pangs of regret at turning his back on McLaren and moving to underachieving Mercedes, they won't have been eased by the recent form of the Brackley team.
In the four races since Hamilton signed his deal - Japan, Korea, India and Abu Dhabi - Mercedes pairing Nico Rosberg and Michael Schumacher have failed to score a point. And despite coming close with Schumacher in the latter race before a puncture intervened, without high attrition, he wouldn't even have been in that position.
During those four races, Rosberg and Schumacher have been marginal top 10 qualifiers, the former impressing on Saturday in India and Abu Dhabi, but faded in the races even when on-track misfortune didn't intervene.
On the plus side for Hamilton, development work has focused on understanding parts for next year, meaning that this rocky patch could potentially lead to the 2013 car being stronger out of the box.
That's the theory anyway...