Besides other kind of endurance tests we do a standard lactate test procedure on a treadmill. You start at 8 or 10 km/h an run for 5 min, then 30 seconds rest for lactate measurments, next step ist 12, 14, 16, 18, 20 km/h each for 5 minutes. You run as long as possible. Good players can run 18 km/h for 5 minutes. They max out her at max hear rate an high lactacte reading 8-15 mmol. Some exceptional players, at the least the ones I tested could run another 2-3 minutes at 20 km/h. No one ever finished 20 km/h. I'm sure there are better players out there, of course, but a 15 min 5 k is a long way.
The average treshold (4mmol) of the german national squad in 1998 was 15,6 km/h. I don't know how threshold was tested. Maybe it was just 3 minutes of running each step which gives higher treshold readings. But germans are always known to be physical very strong and top prepared. If we assume the data is correct then I'm expecting about 18-19 minutes 5k. The median in premier leaque would probably the same, I guess around 19 minutes. And I'm convinced there are premier leaque players out there how can't break 20 minutes.