I cant understand whay that happens.

hello everyone.

I've started play that game less then a month ago, and loved it..
sadly, after several games while I was quality 15.5 I've lost to
people who had the quality of 12 or less.. i thought it was a bug, or any problem in the game.
so, I've started to play again in the first league, and bought awesome players to this level.
now I am in a quality of 19.6, even that most of my players are quality 22+.

in this league, I've lost 4 games and won only 2. let me show you the last game I played against quality of 12.5.

http://s9.postimage.org/4gb9wwhjz/image.jpg

all of his players are maximum quality 14, except of 1 who is quality 20.
or in other words- I am so much better than him.

still I lost 2:1 .

can anyone please explain me exactly how does this game works?