a lot is because the defense will get picked to death and NOT because of the WR's blazing speed. You can put a 4.3 DB on a 4.6 WR and if he lines up in his face another 4.6 WR can get in the DBs way long enough to break the other WR free. BYU is good at this, they are known for it and they do it all the time, especially on LBS to break TEs and RBs free.