Scuttlebutt and forum comments over the past few weeks had Fight Night Champion, the fifth installment of the boxing simulation, as an M-rated title, and gory screenshots certainly seemed to be the reason why. "Mature content throughout," indicates it may go deeper than that.
M-rated sports games are not unprecedented - Blitz: The League and its sequel certainly comes to mind. None, however, have the kind of stature of the Fight Night brand, nor have they been as highly acclaimed. EA Sports assuredly knows its the median age of its user base and took it into account before acting, but this is a bold step nonetheless.