In NFL circles, "luck" can be a dirty word. Players and coaches devote their lives to winning games each and every week, so nobody wants to believe those games might be decided by elements out of their control. Everyone has heard that old idiom about how you would rather be lucky than good, but NFL teams try to be good and hope that whatever lucky elements pop up on Thursday, Sunday and Monday go their way.
"Luck" might be too simplistic to describe what I'm discussing. Some elements of the game are truly random and uncontrollable, like fumble recoveries or the success of opposing kickers.