Hamilton won his third world title with three races to spare. He won 11 of the first 12 poles and 10 of the opening 16 races but his team-mate Nico Rosberg finished much the stronger, with three straight wins and pole position in the last six grands prix. Hamilton last won pole in Monza in September.
Rosberg’s victory in Sunday’s Abu Dhabi Grand Prix, when he finished 8.2sec ahead of a dispirited-looking Hamilton, was the most convincing of his six wins this season.
The Mercedes motorsport director, Toto Wolff, said: “There has been so much discussion about whether Nico has stepped up his game, has the car come towards him or whether Lewis has taken it more easy.
“I think we have to do an intelligent list over the next couple of weeks to try to analyse why. Lewis is still pushing very hard. He is still the same guy with the same talent and putting the same effort into it.”
It could be a number of factors. Rosberg has appeared even more single-minded since being beaten to the championship in Austin in October, when he was furious with Hamilton for being “extremely aggressive” on the opening corner of the US Grand Prix.
Hamilton, who has also admitted enjoying a great deal of partying in recent weeks, could have subconsciously eased off but he is unhappy with the way the car has developed since the Singapore Grand Prix in September.
After again losing out to Rosberg in qualifying in Abu Dhabi on Saturday, Hamilton said: “I have got this great graph which shows you all the races and all 12 of the opening races – apart from Barcelona – the car was great. Since then it has been terrible – terrible laps, terrible balance, particularly on Saturday – so I need to figure that out.
“While it looks like one side has gone a lot better, essentially from our point of view as a team, it’s quite the opposite, I’ve got worse. I said to my race engineer [Peter Bonnington], we really need to sit down to try to figure out how we are going to rectify this.”
Hamilton, who has 21 victories to Rosberg’s 11 over the past two seasons, will still go to Melbourne in March feeling confident he can rediscover his old ascendancy for the start of the 2016 season but he will feel much better if he can work out exactly why his form has faltered.
Wolff said: “After Singapore we developed in a different direction and whether the car has come more towards Nico and gone away from Lewis, I don’t know. It could be a factor but I wouldn’t want to reduce it to one single reason. It could be many possible factors.”
Sir Jackie Stewart, tied with Hamilton as Britain’s most successful driver with three titles, hopes Rosberg triumphs next year. “It would be good if Nico won the title. That would be very good,” Stewart, 76, said.
He added: “There is nothing to stop Rosberg winning. He is quick. We have seen him have so many pole positions. He is smoother than Hamilton. Lewis is quite aggressive. He has won more races because of that aggression but sometimes that can bite you also.
“Nico is good, there is no question about it. The trouble is you have to be very good and he has got to just step up that little bit extra.”
guardian.co.uk © Guardian News and Media Limited 2010