Alexander Keir, 38, was discovered injured in Bromley Road at around 2am yesterday.
A member of the public found him and alerted the ambulance service who took him to Blackpool Victoria Hospital.
However, Mr Keir’s condition was such that he was later transferred to Royal Preston Hospital where he underwent emergency surgery.
He is reported to be critically ill and his family remain with him at the hospital.
Police said the last known sighting of Mr Keir that they are aware of was at about 9pm on Riley Avenue on Tuesday 4 August.
Detective Inspector Paddy O’Neill of Blackpool Police said: “We need to ascertain how Alex came to suffer his head injury, and would ask anyone who can help us to make contact. At this stage we remain open-minded as to what happened and it is unclear whether he was subject to an assault, a fall or whether he had some sort of medical episode.
“Alex is white, about 6ft tall aged 38.
“He was smartly dressed in a dark suit and tie with a black shirt.
“We need to establish his movements between 9pm last night and 2am in the morning when we believe he was in the St Annes area.”
Anyone with information should contact police on 101 quoting log number 0088 of August 5.
Alternatively, Crimestoppers can be called anonymously on 0800 555 111 or on-line at Crimestoppers-uk.org.