Funny what I was about to post and you suffering a hammy injury playing basketball (age probably was a factor). I was about to say the sudden stop/start 100%/0% nature of football is conducive to hamstring injuries. If you follow the NBA, hamstring injuries are relatively rare. NBA players are in constant motion and don't generally do the same kind of sudden acceleration that NFL players do (WR/CB/RB mostly).

My personal theory is that players need to keep moving and keep muscles warmed up as best they can. Its not about stretching as much as it is about just keeping it "ready" or warm.