A Myth (or an advice) is saying that you mustn't accept a friend request from a team you 're playing in the same competition.
With that way, your friend/opponent can organize a friendly game with your team and learn how to play in the between official game.
Well, that's a myth.
Friendly games have different calculations than the official games and in general, a t11 game never is the same again.
There are too many factors that affect it and it various every time.
You can see an example in the Mythbusters lab here, post #9
http://forum.topeleven.com/top-eleve...sters-lab.html

Beyond the Myth :
I try not to make friends from my competitions. The reason isn't that the other manager will discover my secrets but because (probably) I 'll have to support him in some games and I don't want the other teams to misunderstand that (because they don't know we 're friends).
Another reason is that my "friend" 'll know my games schedule so he could switch our game in an inconvenient for me hour.