If they lose to Brighton today, it won't be surprising either, Brighton are in great form, they beat Newcastle and Manchester United, and are currently third in the standings, so you understand everything.
Today's match is going to be a tough one for Chelsea against Brighton because Brighton seems to be very inform this season as of there last seven matches they have won five which is a good start, but there match between Manchester United was the one that got me surprise because I never believe Brighton will draw the match let alone win Manchester United 3:1, so putting there performance they had against Manchester United to Chelsea match today is going to be tough on Chelsea and also Chelsea cannot afford to lose this match after what happened to them against Aston Villa, they will try as much as possible to either win or draw.
Brighton is a stumbling block for other clubs, especially if with the current state of Chelsea, of course it is very possible for Brighton to beat Chelsea in this match. I will not say this match is a match of proof from Chelsea, because even if they win it is what they should get if their situation is not like now. But will they be able to do it? Honestly, with no intention of demeaning Chelsea, I doubt Chelsea will be able to beat Brighton even though they will play at their own headquarters, Stamford Brigde.