As a general question, I always wonder how they prepare this sort of change of style/approach. The idea is usually that managers have a general game plan, and that training drills repeat key situations so often, that they become second instinct by players. That way, they make the right moves automatically on game day, reducing the number of split second decisions they need to make. That's why the Plan B of a well-drilled team is usually a lot like Plan A: you can't just ask players to change to a different set of automatisms mid-game.
So how does that work for a defensive shift to 'see the game out'? I get how adding replacing players who focus on attack with players focusing on defense necessarily pushes the team backward, and packing your own half makes attacking harder for the opponent. But if you break up patterns and automatisms, won't players get confused more easily, leading to more flaws and errors for the opponent to exploit? I also doubt managers train on two distinct sets of patterns, as that's confusing as well. So except if the current plan is failing or players are getting really tired, is shifting into a defensive mode ever a good idea?