The first reports suggest Ranger broke the man's jaw and knocked him unconcious.
Ranger is on the transfer list and knocked back a move to Blackpool last month after both clubs agreed a fee.
Police are appealing for witnesses following an assault outside Cosy Joes Pub, in Groat Market in Newcastle city centre.
It happened at 1.30am on Saturday, August 27, when police were called after a 33-year-old man was assaulted.
When police arrived the injured man was unconscious and was taken to the Royal Victoria Infirmary suffering from a suspected broken jaw.
Ranger made off and police carried out a search of the area.
He was arrested a short time later, nearby, on suspicion of
assault and is currently helping police with their enquiries.
Police are appealing for anyone who was in the area at the time who may have seen or heard anything suspicious to contact them.