Guys like Rice, Irvin, Fitz, and Chris Carter had one thing in common; work ethic.
They were students of the game in creating separation and hitting the weight room.
The old adage was 'game speed'.
Those guys also had some of the best concentration/focus I've ever seen as well. Not just getting creating separation and getting to the ball, but the focus to CATCH it, even when getting raped by the DB. They were going to catch the ball simply by outworking the other guy, nothing more.
Braxton had a bit of that. Wasn't fast, undersized. But there was a reason he was our kick returner. Excellent focus and concentration. That's pretty much kept him in the NFL so far.