I disagree.
Zagreb sat back all game, at times we only had the 2 CBs and Cech in our own half and that's why we got caught on the break in the first half. West Ham sat back too.
When you say i haven't seen teams sit back in a long time, you only have to stretch back to April when Swansea, Sunderland and some other team i cant remember came to the Emirates and sat back throughout the game.