Jenson Button says after Sebastian Vettel's form last year as well as Ferrari's, he has been surprised by the German's pace this season.
Vettel joined Ferrari on the back of a dismal final season with Red Bull Racing in which he failed to claim a single race win.
Moving over to the struggling Scuderia, many believed it would take months – if not longer – before the partnership began to see results.
However already, just six races into this season, Vettel has racked up five podium finishes one of which was the race win in Malaysia.
And his form has come a surprise to Button.
"Sebastian for four years did an amazing job and a lot of people said it was the team around him doing a great, he just had to finish it off," the McLaren driver told F1i.com.
"Then Daniel in England we would say 'put some manners on him', but basically did a better job than Sebastian did last year. A much better job, he won three races, Sebastian won no races, so his stock dropped massively I think.
"He did the right thing to move teams and he's gone to Ferrari and he seems to have done a very good job. So to win in his second grand prix with Ferrari is very impressive, obviously the car is a very good car now compared to last year when Fernando was driving it but it's amazing how things change around for teams and for drivers. I didn't expect him to be so quick at Ferrari."