The 25-year-old was visiting a bookies in Thornliebank, East Renfrewshire, when he was targeted in Kennishead Road just before 5pm on Friday.
The victim had parked his white Vauxhall Astra in a lane next to the William Hill bookmakers before going in.
When he returned to his car, he was app-roached by a man who then hit him in face with a sharp implement.
The suspect then walked off in an unknown direction, while the victim went to a nearby bowling club to raise the alarm.
Police and emergency services were then called to the scene and the man was taken to Glasgow Victoria Infirmary to be treated for a severe injury to his face.
He was then trans-ferred to the Southern General Hospital where he is now in a stable condition.
There is no descript-ion of the thug and police are appealing for information or witnesses to trace him.
Detective Constable John Dowds, from Pollok CID, said: "This was a horrifying attack in the middle of the day, in a busy area of Glasgow.
"Our inquiries are ongoing, however I would like to stress that we are not treating this as a random attack.
"I would like to appeal to anyone who was in Kennishead Road at around the time of the incident.
"At the time of the attack, the area would have been busy given that it was a Friday evening, and I am hopeful some people may have seen a man acting suspiciously around the bookmakers prior to incident or immediately after."
Anyone with information is urged to contact Pollok CID on 0141 532 5600 or contact Crimestoppers, anony-mously, on 0800 555 111.