"While Arsenal celebrate a victory which Arsène Wenger will offer as proof that this is a team whose moment has come at last, Chelsea will be wondering if last night was the moment at which a dip turned into a decline. A return of six points from a possible 24 in their last eight Premier League games, and no wins in the last six matches, suggest that something has gone badly wrong for the champions in recent weeks."
I wouldn't say they are in decline, they're just experiencing the compounded effects of both injuries and loss of form to the players who are always first to be put on the team sheet, something Arsenal knows all too well.