http://www.seahawks.com/12th-Man/
http://en.wikipedia.org/wiki/12th_man_%28football%29
The 12th man or 12th player is a term for the fans within a stadium during American football and association football games. As most football leagues allow a maximum of eleven players per team on the playing field at a time, referring to a team's fans as the 12th man implies that they have a potentially helpful role in the game.
普通球隊只有11個人在場地打
第12個就是指球迷
也就是中國人所說的我的(球迷）精神與你們（球隊）同在