Hamilton has finished second behind Rosberg in Mexico and Brazil after wrapping up his third world title with victory in the United States Grand Prix last month.
The Brit has alluded to his W06 not being as effective as it was earlier in the season, but Rosberg said his recent success is not down to mechanical factors.
"I'm not really sure what he is referring to, but there is no change in the feel of the car or anything." he said ahead of the final race of the season in Abu Dhabi this weekend.
"For me it was always very close before and now it's just swung the other way. It's very close but I'm ahead now and I'm quicker and that's it.
"Last year I was quicker in qualifying and the beginning of this year I was not and now I am again, so it's just been toing and froing a little bit and at the moment I'm the one with the upper hand."
Rosberg secured second place in the drivers' standings with his victory at Interlagos last time out and will be eyeing his first victory at the Yas Marina Circuit this weekend.
