So just a counterargument for argument’s sake. We were also playing 3 at the back when we beat PSV, playing 3 at back when we beat Almería, 3 at the back when we beat Fenerbahçe, etc. So I get that maybe the system wasn’t the optimal tactical strategy on paper, but I just don’t get why there is some orthodoxy that says what the right formation and wrong formation is. The right formation is one that wins, the wrong formation is the one that loses.
So you can say that the formation wasn’t winning reliably enough to be a smart choice, but it seems illogical to me that the choice to field three at back was somehow a crazy, heterodox choice which any smart person knew couldn’t work given his option set.