Jenson Button has said that Nico Rosberg will be surprised by his new Mercedes teammate Lewis Hamilton.
Button told Autosport.com: "I think he'll probably get a bit of a surprise. I know he's been his teammate in the past, but I think he'll be surprised at how Lewis can get performance out of a bad car.
"It's been a good three years and it's amazing how quick those three years have gone by. It's been a good partnership.
"We've had quite a bit of fun in terms of racing over those three years."
Sergio Perez will replace Hamilton at McLaren.