Officers were called to Portswood Road at around 4pm on Monday, August 22 after receiving reports that a 28-year-old man had been stabbed outside the KFC restaurant.
A knife was recovered nearby.
Detectives are currently trying to piece together what happened and understand that the man was stabbed on Vanguard Road, Midanbury, before driving to Portswood.
He is currently at Southampton General Hospital undergoing surgery for what are said to be life-threatening injuries.
A section of the pavement on Portswood Road, and part of Vanguard Road, were cordoned off to allow police to investigate the scenes. According to the Daily Echo, "four armed units and two dog units were among dozens of officers searching the area for his attacker".
Anyone with information is asked to contact Bitterne CID on 101 or the anonymous Crimestoppers charity on 0800 555 111. Minicom users should contact 01962 875000. Send a message direct to a police officer using an online messaging system here.