Dude I'm pretty sure football takes willpower...people have been telling you all season "you're too small" or, "you're too slow". it's the 4th quarter, you have a headache, you're tired, you are down by 6, not to mention how you are beaten the fuck up because you have gotten 30 carries so far in the game, you probably have a concussion but you could give a flying fuck because theres 1:05 left in the game and you have to score a touchdown next play...you are tired as fuck, your muscles don't wanna go any longer but your mind has to keep telling your muscles to keep sprinting no matter how badly you wanna jog, because in the end you know it's all worth it when you put up a W and to prove haters wrong.
Football takes no endurance?
Oh and if you have ever sprinted 10 huge hills in a row you will understand exactly how tiring it is when you have to keep up with and beat the skill players who run 4.5's. If you have ever run 10 gassers (sideline-sideline-sideline-sideline) in under 38 seconds each time you will understand how tiring football is. That's in full pads by the way which is (without the helmet) 8 pounds total. That's just conditioning. When you get to gametime its worse because you REALLY sprint 100% on every single play in order to be successful.
Football involves a stop and go full sprint endurance, not a long distance endurance like xc or soccer.