Button knows theres still pressure on him to produce that truly winning Champions drive. Yes he did have a good Brazil GP but he also was very lucky, he made good passes but they were against amateurs for the most part and he's in an awesome car so that always helps.
He still hasn't won since June and ge needs to win this GP to show he's no joke, everyone who is a champion always deserves it, but he's certainly not one of the great champions. I'd go as far as saying he's a champion based on circumstances rather than driving talent..