You also have to prove that Green knew at the time of the firing that Kendall was one of the players that filed a complaint. It's not enough to just say "Well I filed a complaint and now I am jobless". Your employer has to know you filed the complaint in order for the "He fired for filing a complaint" argument to hold up.
I understand that in all likelihood Green knew Kendall was one of those that filed a complaint, but you still have to prove he knew this at the time of firing. My guess is that the front office gave Green this information at that same source isn't going to come out and say "I told Green before he released Kendall that he was one of the ones who complained".
But hey, this is the land of crazy lawsuits prevailing, so anything is possible I guess.