Toto Wolff has suggested Lewis Hamilton may have 'unconsciously' let the intensity of his driving slip in the closing rounds of the 2015 season, but says Mercedes will address his concerns of a 'change' in the car.

After wrapping up his third world title in the United States, Hamilton has been comfortably out-performed by team-mate Nico Rosberg since then, with the German winning the final three races in Mexico, Brazil and Abu Dhabi with pole-to-flag performances.

With Rosberg - who ended the year with six straight pole positions - owing the turn of form to his development as a driver, Hamilton offered a different justification, claiming a change to the car's set-up since the Singapore Grand Prix has worked against him.

With Hamilton suggesting his form has gotten worse as a result, rather than Rosberg's getting better, Wolff is more sceptical about the three-time champion's words, reckoning a combination of factors could be at play, including him 'taking it easier' having wrapped up the title.

"There has been so much discussion about whether Nico has stepped up his game or if the car come towards him development-wise, or has Lewis just taken it more easily unconsciously.

"I don't think it is something that would happen consciously. I believe he is still pushing hard and he is still the same guy with the same talent putting the same effort into it. You will have to ask him but it could play a role.

"We have to do an intelligent list in the next couple of weeks to analyse. I think we have to find out, at the end of the day for Lewis the world championship title mattered but then those last couple of races saw really great driving from Nico."

Regardless, Mercedes says it will look into Hamilton's concerns about a change in the car, but says it would be a 'soft factor' not necessarily clear in any data.

"I think it is more a soft factor, maybe not as easy to grab with data. I agree, the drivers are very much part of the package to function and Lewis mentioned a couple of days ago he didn't feel the car was as good as it was before and if he says that it is something we need to consider and see whether we have data support for that or not. Whatever the outcome is we will discuss and see what we can do."