I wasn't too happy when I saw the formation, as we shouldn't be playing against the bottom club at home with 5 defenders across the back. I always look to see wingers as wingbacks should only be supplements, not replacements for giving us width.
Its about attacking in numbers. Look at Man City, Liverpool etc., when they are attacking you see 8 or 9 of their players in camera shot around the penalty box. Not one striker and a couple of midfielders.
On a related reason, I think if there is one player Billic tries to guarentee a place, its Ivanovic. When Billic first made contact, I expect he said, look I want the defence to be built around you. Trouble is, Ivanovic is slow, so he needs extra help and maybe that's why we are playing 3 central defenders instead of 2.
The only reason we should be playing without wingers is if they are all off form. Maybe that was the reason and seeing as we won yesterday, now is not the time to criticise him.