I don't think I've ever watched a whole one, despite growing up in a house where the TV was usually tuned into either football or baseball, both of my parents being sports fans (they met at a game where my mom was playing softball). The only sport I ever got into, briefly, was tennis when Borg & McEnroe were going at it.
In high school I did spend a lot of time on the sidelines with my camera, soaking in the cool night autumn air, watching the weekly dramas while not really caring who won. (I also enjoyed
Friday Night Lights.) Mostly organised sports drive me crazy with all the stops and starts.
My brother-in-law's father was a professional football player – a defensive lineman, I see from his Wikipedia page – for the Cleveland Browns and a few other teams. He was BIG, and died relatively young of a heart attack.