The 2008 world champion told Autosport: "Something gave way on the right-hand side of the car. I was going through the chicane and it snapped out. I tried to pull away and it wouldn't move, so something's busted.
"This is a very difficult circuit to overtake on so being at the front means everything. Hopefully we can get a good start and maybe still challenge for podium positions. I'm just grateful I didn't drop too far down."
Red Bull's Mark Webber will start from pole at tomorrow's race.