US GP Sunday quotes: Williams

"I could not pass Tonio because I could not attack as my car was quite difficult to drive today with a lot of fuel onboard. I'm now looking forward to Magny-Cours."

Nico Rosberg - DNF: "I was having a really solid race and was happy because I thought sixth place was in the bag. We were on a good strategy and the car was going well. We've shown that we've made some progress on performance and we would definitely have been in the points today.

"I can't be so angry because I drove really well. It will go my way another day, I'm sure of that. Sometimes things go wrong, that's just the way it is and I have to accept it."

Rod Nelson, Chief Operations Engineer: "Today's result is obviously hugely disappointing for the team. Nico drove a storming race on a one stop strategy, which was the right thing to do. He had no tyre problems or any other issues. Unfortunately, he was held up quite badly by back-markers and we really struggled to get enough blue flags out for him in time.

"It looked like it was going to be an easy sixth place but then an oil leak struck in the last few laps. The cause of the leak is currently under investigation. Alex had a cracking start, but he was caught up behind Liuzzi with no way past.

"Both drivers gave great performances and today we were looking for two points-scoring finishes. It wasn't to be, though. We will now look into the failure on Nico's car and ensure it doesn't happen again and look ahead to the next race."