He remains in a serious but stable condition.
Police had to close the road in both directions near to junctions towards Castle Donington and Loughborough, to allow an air ambulance to land.
A Leicestershire police spokesperson said:
"Officers were called at 7.30pm yesterday (Tuesday) to the A42 near Breedon on the Hill following a report of a 19-year-old man who was found injured near to the road.
East Midlands Ambulance Service were in attendance and the man was taken to hospital with serious injuries.
He currently remains in hospital where his condition is described as critical but stable.
Enquiries are ongoing to establish the full circumstances of the incident."