I know this isn't very credible, but I just created two players on Madden. I gave one 99 SPD and 99 ACC and the other 99 SPD and 0 ACC. Then I went into practice mode and ran them both from the 40 yard line to the endzone and timed it with an online stop watch (One hand on controler, the other on the mouse) and they both ran 4.6 almost every single time. You honestly couldn't even tell the difference.