Mercedes AMG Petronas
Nico Rosberg believes that Mercedes must improve its race pace ahead of this weekend's Italian Grand Prix at Monza.
The championship leader set the pace during Friday's second practice session but Rosberg fears that Mercedes's rivals are closer than they have been at recent events.
"It's been a good day, but the others seem a little bit closer," he said. "Our car seems to be better on one lap than on the long run so it's the long run that we need to work on. I think we still are looking very, very good but we need to work hard this evening to optimise everything."
Rosberg also conceded that he did not feel fully comfortable in the W05 Hybrid during the session.
"I didn't feel 100 per cent confident in the car, so I can't be happy with today and I have a lot of work to do tonight with the boys," he concluded.
Team-mate Lewis Hamilton was second fastest, 0.061s behind Rosberg, but missed the first hour of the second session due to an electrical issue.
"I felt really good after the practice session this morning and we have definitely got a competitive car this weekend," he said.
"Unfortunately we lost some track time this afternoon but the guys did a great job to get me back out so I got a few laps at least. We made some changes over lunch and then another during the session and, although I didn't have a lot of laps, the car feels great."
