Catching the ball is all about desire. It's that simple.
Let me be careful not to let anyone know that I am making a "generalization" or a wicked statement but look at two players...Fred Blinetkoff and Art Monk. These guys didn't have jets in their heals but they could get wide open on any occasion. In Fred's case, it was mad crazy how he would get so wide open. Many times, there wouldn't be a defender in the picture for four yards.
It was because he knew how to run pass patterns to perfection. If it was a ten yard pattern he ran a ten yard pattern, not a 10 1/2 or 11 yard pattern
Route running is what gets you separation in the NFL majority of the time. Ginn in college got by on physical ability & did not have to work on route running. Its something he is having to learn to do while on the job. Many of a college Wr does when they arrive in the NFL & that is why the 3rd Yr rule is talked about for Wr in the NFL.