Sometimes I get the feeling that the game engine has decided what the optimum formation, tactics and orders are the 'best' for you for that match and you have to guess what they are - once you have found them you get a really good performance and result.
For instance, recently in a match I was much better Quality than the opponent, but they were leading 2-0 and I was in for a right old Trolling. I noticed that the two opposition wide defenders had high match ratings, so switched to attacking through the centre exclusively, instead of mixed - into a 3DC-DMC central defence, which in normal circumstances was a complete no-no. I won 4-2...