The 2008 world champion starts ninth on the grid after spinning on his final lap in qualifying, while teammate Nico Rosberg could only manage third, preventing the constructor from securing pole position for the first time this season.
The Briton told BBC Sport: "It was just two not very good laps. Or one-and-a-quarter-laps, I didn't finish my second one.
"The feeling was there in the car, it has been good all weekend. To be honest my first lap was looking good and went wide in the second to last corner, I think that lap would have done it. I've swallowed that [pill] many times, it's easier the more and more you do it.
"We're going to be strong tomorrow, it's going to be very, very hard from where we are, but of course I'll do everything I can to try and get some good points for the team. It's damage limitation I guess."
Williams's Felipe Massa will be on pole for the first time since 2008.