Skill Transfer

In the Houston Texans conditiong manual there is a section on skill transfer, and in that section the author uses jumping rope as an example. He states that jumping rope will give an athlete a cardiovascular workout, and help him jump rope better, but not improve foot speed or on field performance. If this is true, then wouldn't the same hold true for dot drills and speed ladders? I'm not sure if I buy into the idea that these drills won't help foot speed or on the field quickness. He says that the only way to improve quickness on the field is to practice your individual techniques (ie; backpedaling, routes, cuts, etc.) Wouldn't it be darn near impossible to practice every cut and direction change that a player goes through the course of an entire game? I mean it is possible that during the entire course of the game a defensive back will have to slightly alter his technique on every single play, due to the change in the routes run by the receivers and a whole host of other variables. What do you guys think about skill transfer and how speed ladders, ropes, cone drills, jumping rope, or any other drill you use affects on the field performance?