Hey have you had 20+ shots on target and 65% possession? Can't beat their 70 rated goalkeeper because we've given him a stat boost because his team is worse than yours? Well at least we're going to let them score every time they push the shoot button, even though you have the best goalkeeper and defense in the game.
I've lost 8 games on Ultimate Team (currently on 108 wins), not one of them was by more than 1 goal, and most of them were 1-0 wins for the opposition, with a 90th minute header, their first shot in the entire game. EA claim they don't buff or nerf anyone, but they mention this mysterious moral and chemistry system. Essentially what they do is, if you're dominating against a team worse than yours, they will throw in the FA Cup curve ball, that special thing that makes league 2 teams beat Premier League teams. So suddenly all your hard work is wiped out by a chemistry and moral boost for the other team. You don't get it so much in Ultimate Team, but if you've ever played Pro Clubs then you know exactly what I'm talking about.