What I find interesting about American Football is that the QBs are considered rivals, despite never being on the pitch at the same time. Messi and Ronaldo actually appear on many images contesting the same ball, Peyton and Brady you'd struggle to find pictures other than the post-match handshake.

Why isn't the rivalry considered to be between the QB and someone on the defense? There's actually two matchups in an NFL game (plus specials but whatever), the two offense versus defense pairings. It's odd to make the rivalry about two guys who aren't directly tackling each other, when there are people on both teams who really are tackling those guys.