Strength: Strength you need to play any position! The Quarterback needs strength to throw the ball as well as handoff or run. The offensive lineman needs strength to block the defensive players who are trying to sack the Qb. The defensive players need strength to tackle recievers and running backs, and to sack the QB, as well as intercept the football.
Running: Running is everything in football- from the offensive line all the way to the safety. You need to be fast to play football, especially if you are a running back or wide reciever. And, running is the only way to move in football.
Mental Ability: 99% of football is in the mind. If you think that you can do it, you can. If you think that you will be the best reciever ever, chances are you might wind up that. Attitude towards football is what matters. Be tough, use your head, and play football!