Rosberg laments troubled start

"It was a difficult day for me because I came out of the pits very late in the second session due to a gearbox problem," said Rosberg, who was making his debut at the Montreal circuit.

"I did just ten laps which is not quite enough for me as it was my first experience of this track. Luckily however this circuit doesn't seem too difficult and the car felt alright. It will be better tomorrow, after some more running."

The Williams driver finished 21st, 14 position behinds teammate Mark Webber, who predicted an interesting task in choosing the right tyres for the weekend.

"So far this weekend looks like it's going to be interesting on the tyre front," said the Australian. "The grip level is very low on the circuit and of course both tyre companies made their choices a couple of weeks ago.

"It went a lot better for us in the second session and it's good to get a bit of temperature in the track, this will certainly benefit us.

"We've got a lot of information to go through tonight from Alex's car and my two runs. All in all it's been an interesting day which threw up a lot of things we didn't expect, but we will cope with that tomorrow."

The team's third driver Alex Wurz was third fastest.