I was a decent soccer player in club and high school, even playing for the same club as one of the current starters for the US. However, as we all developed physically it got to the point where most coaches agreed that I did not have the top speed to play at the next level. I went on to a decently successful D1 career in xc/track, focusing on the steeple and 5k, but getting my 1500 down in the low 3:50's (about 4:10 equivalent). I was not a big kicker, but I wasn't severely limited by that either. In college I hung out with the soccer guys a good bit, and got a sense of their aerobic training. I would say there is a good 5-10% at the highest level who could run under 4:20, and maybe a few outliers who could break 4:10. These would tend to be the midfielders in the 150 lb. range. If 8-12 months were dedicated to base mileage and then specific training, I would say almost all of those sub-4:20 guys could cut below 4:10, and we might see one or two sub 4:05's. These are clearly tough predictions to make, but the talent is there.