This result coupled with the euro drubbings will no doubt have knocked their confidence. They're still clearly the best team in the league but getting horsed will affect any team.
I was just thinking that I couldn't recall a time when either of the cheeks had been beaten by four goals by another Scottish team (omitting OF games). I remember that the DABs won 3-0 at Ibrox in the early 90s and Hibs beat them there by the same scoreline in 2006. I don't recall Celtic taking a heavy defeat since we humped them twice in 90/91.
As I said, we shouldn't be fearful of a backlash. A backlash is a response to a bad day at the office. Celtic are suffering from a real dip in form. It's up to us to exploit that.