The difference is these guys are running non stop for 80 mins, you quickly lose any speed you have had.
The reason they don't just give it to the backs to run around the defense, is the way the defense is structured, it is very hard for a back to get round 12 guys they way the defense is schemed.
They need to set up plays to create lanes for the backs to take advantage of, which is very hard when there is no play clock
Generally the big strong forwards take a lot of defense guys to stop them, extra men in the tacke.
Extra men in the tackle, creates space and lanes for the quick men
[ Edited by JaGuR on Oct 4, 2015 at 2:42 AM ]