Lewis Hamilton reckons that Ferrari has caught up with Mercedes over the winter and can put up a "good fight" at the front of the field in Formula 1 this year.
Mercedes has won the last two constructors' championships with relative ease, winning all but six of the races since the beginning of 2014, while Hamilton has only had teammate Nico Rosberg to contend with for the drivers' title.
Hamilton enters 2016 chasing a third straight championship, and although he was elated with the new Mercedes W07 car's running during testing, he remains very wary of the threat posed by Ferrari.
"The winter tests went fantastically well, and our new car is absolutely incredible. I never thought that we would be driving quite so many kilometres in preparation," Hamilton said.
"We were with the team yesterday and congratulated everyone involved on this great Silver Arrow. This is a real team effort from all our colleagues in Brackley, Brixworth and Stuttgart.
"Nevertheless, I'm expecting this season to be an uphill battle. Ferrari have caught up and Nico is always a strong opponent.
"I believe that we have a good car, but Ferrari were posting some impressive times during the tests – both on the fast laps and on longer runs.
"We are certainly in for a good fight, but after all that's exactly what everyone wants. In any case, I'm looking forward to it very much."