The gap-toothed smile, Frank, I think David is referring to.
That, and cauliflower ears, are trade-marks of the game.
American football??? choreographed set pieces, with occasional flashes of good and inspired play, and more padding than a pantomime dame.... and those forward passes?
Rugby??? Similar balls, but improved by flowing moves, crashing tackles, Garry Owens, a damn sight less money, more balls, and brilliance, and usually at club level, a good social camaraderie, and friendships for life.
Football??? Spherical balls, cynical tackles, theatricals, prima donnas, and lots of money.
May not be an accurate summary, very biased, actually, but to go further...