Wide receivers: 20-yard split
While the 40-yard dash is among the most effective measuring sticks, the 20-yard split on the 40 tells scouts how quickly a prospect can get to full speed, which is critical to gaining separation from defensive backs off the line of scrimmage. Marques Colston ran a pedestrian 4.55 in the 40 at last year's combine at nearly 6-foot-5 and 224 pounds, but his 20-yard split time (2.62 seconds) was among the best of the five receivers who ran. Considering his success as an NFL rookie maybe more stock should have been placed in his initial burst rather than his top-end speed.
http://insider.espn.go.com/nfl/draft08/insider/columns/story?columnist=mcshay_todd&id=3259921