40 yard times are an indication but are unfortunately somewhat like star ratings. Not the best metric. For example Instinct, recognition, vision, burst, acceleration, ability to cut at high speed, ability to move fast laterally with shoulders square, and ability to take the proper angle is far more indicative of good football play than a 40 yard time. There are lots of great football playmakers with less than impressive 40 times and lots of fast players, judged by 40 times, who are only average football playmakers.