User blog comment:IamJakuhoRaikoben/Chapter 313: Champion's Scenario, Review./@comment-4933386-20130104161355

Maybe Sting will tell Fairy Tail what Minerva's magic is and her evil plans... and then Minerva will be the first person to attack their own teammate(Sting). Then Erza(the one is gonna win) will be angry of why would Minerva attack her own "nakama" then... yeah Minerva loses...

That's my theory.