The man, aged in his mid-30s, was found in an alley on Friday night between St Aubyn Street and Keadyville Avenue by a member of the public at around 7.30pm.
Detective Sergeant Mason said: “The man suffered facial injuries and was taken to hospital for treatment, where he remains.
“His injuries are not thought to be life threatening at this stage.
“We are appealing to anyone who knows anything about the incident, or anyone who was in the St Aubyn Street area between 7pm and 7:30pm last night and noticed anything suspicious, to contact detectives at Musgrave Criminal Investigation Unit on the non-emergency number, 101, quoting reference 1302 of 22/09/17.
“Or information can be given anonymously to Crimestoppers on 0800 555 111.”