My girlfriend just had the first cup match of the season, with both her and myself watching and it being a home match she had a +15% possession rate. Their teams were pretty evenly matched before the possession bonus, so in theory with that 15% bonus she should have dominated the match... and at first she did. She scored the first goal fairly early.
Then in the second half her opponent (the manager wasn't there) had a friend come and support him, he was in club level 13 (where as the match was a club level 4) All of a sudden, after this guy turns up to support my girlfriends opponent his team started to completely dominate the match! the 2% bonus that he should have got from having a friend support seemed to be more like a 200%. In the comments section it went from a pretty even spread of who was doing what in the match to being totally taken over by what my girlfriends opponent was doing... all because a level 13 came to watch a level 4 game.
I can not and do not believe this was pure coincident that this guy shows up then all of a sudden the team that was losing fairly suddenly becomes an unstoppable football team that wins 3-1. This is just another example of how this game is completely rigged!