An unwritten rule amongst players is not to publicly criticise a team-mate because one day it could be you who's the villain.
That's why when Celtic's Kris Commons spoke about Efe Ambrose's performance immediately after the 3-0 Champions League defeat to Juventus, I was a bit perplexed.
Has he never had a bad game or missed a chance that has cost his side points?
As the saying goes, "win as a team and lose as a team".
Well, Commons showed himself an exception to that and his comments wouldn't have gone down well in the Bhoys dressing room, that's for sure.
Celtic manager Neil Lennon publicly backed both players in the press though I'm sure that behind closed doors he had stern words for Commons.
Ambrose knew he didn't perform to his usual standard but maybe if Commons had scored with one of his many efforts at goal the scoreline may have been different. Of course that wasn't his fault!