Nico Rosberg, 2009Nico Rosberg is disappointed to be starting only sixth on the grid for Sunday's Monaco Grand Prix.

The German Williams driver admitted he failed to capitalize on the potential of the FW31 and blamed it on a combination of being held up by Rubens Barrichello and his car's poor balance.

"The first two sessions went fine today, but I was not happy with the final conclusion in Q3," said Rosberg, who was quickest in practice on Thursday. "P6 was not where I wanted to be and it should have been better.

"I had some balance problems in the last run and some traffic, particularly with Barrichello on my fastest lap, so I didn't manage to make the best of the circumstances. Anyway, that's the way it has played out and we just need to make the best of it."

Teammate Kazuki Nakajima equalled his best qualifying performance (Singapore 2008) by placing 10th on the grid.