Nico Rosberg admitted that his final race with Williams was a disappointment, but was pleased to clinch a career-best seventh in the drivers' championship.
The German finished just outside the points in ninth place today, having been jumped by the one-stopping Kamui Kobayashi.
"It wasn't a terribly exciting race for me today as I just didn't have the pace to do any better," he said.
"From a personal perspective, my seventh place in the drivers' table wasn't challenged and I think this was a good result this year in the circumstances.
"It's been a long season and I would really like to thank all the team for their effort during the last four years.
"We have had a great time together."
Rosberg confirmed earlier this weekend that he is to leave Williams after four seasons, and is expected to join Brawn.
Williams is tipped to announce current Brawn driver Rubens Barrichello and GP2 champion Nico Hulkenberg as its 2010 drivers in the coming days.
With neither Williams scoring as Kazuki Nakajima had an anonymous run to 13th, BMW managed to move ahead into sixth in the constructors' championship thanks to Nick Heidfeld's fifth place.
Williams had been 20 points clear of its former partner with six races to go, but then lost some chances to score well - notably when Rosberg's pit error in Singapore and transmission failure in Brazil cost the team potential podiums - just as BMW finally found some pace.
"It was naturally disappointing not to be able to retain our championship position today, but well done to BMW and we will miss them next year," said Williams's chief operations engineer Rod Nelson.