Kavan Brissett, agedÂ 21, was knifed in his chest inÂ an alleywayÂ off Langsett Walk, Upperthorpe, on Tuesday, August 14.
He was rushed to hospital and underwent emergency surgery but diedÂ four days later when his life support machine was switched off.
Detectives are treating the stabbing as a '˜targeted' attack butÂ have not yet revealed the motive.
But today South Yorkshire PoliceÂ revealed that the death is '˜not being linked to any other incidents'.
Four arrests have been made over the murderÂ but nobody has yet been charged.
An 18-year-old man was arrested on suspicion of attempted murder and three boys -Â two aged 17 and one aged 16 - were arrested on suspicion of conspiracy to rob.
TheyÂ have all been bailed pending further enquiries.
Detectives are also trying to trace 29-year-old Ahmed Farrah, who has links to Broomhall and whoÂ is believed to hold vital information.
He is said to know he is wanted for questioning but is actively evading arrest.
South Yorkshire PoliceÂ has warned that anyone shielding himÂ faces prosecution.
Anyone withÂ informationÂ should call South Yorkshire Police onÂ 101 or the incident room on 01709 443507.Â