Don't assume that's how he will play in the real match.
I've seen other managers put their teams in weird formations between matches just to keep their opposition guessing, and change it with a couple of minutes to go before the 3 minute warning - have a look then and see what he's about. If still no clue then set a good general purpose formation - 4-4-2 Classic or the like - and then react once the match has started and you've seen his actual formation.