I had a similar problem, I just lost a Champions League match against an opponent who was 15% weaker than me. When comparing the results of our players, the rating of mine where 72,7 so average 6,6 and my opponent had a 62,5 so average of 5,68. My attack was more than 12% batter and I played an attack game. I really do not understand this result.
I am really frustrated. Thank you for your help.