A 44-year-old man remains critically ill in hospital with head injuries following an incident in the city centre.
The man was walking his Rottweiller dog in King Street at 4.45pm on Wednesday when he became involved in a row with one of a group of young black men.
Police said the man fell to the ground and suffered a head injury.
He is being treated at the Queen's Medical Centre in Nottingham, and was said to still be in a critical condition yesterday.
A 19-year-old man arrested in connection with incident on Friday has been released on police bail.
A worker in an office near the scene of the incident, who asked not to be named, said: "I heard a scream and when I looked outside I saw a bloke on the floor with his dog next to him and people trying to help him.
"He was out cold for at least 10 minutes. He was still holding his dog's lead and the dog was just sat there."
Anyone with information is asked to call police on 101, or Crimestoppers, on 0800 555111.
