The incident took place at around 2.30 pm on Friday when the 51-year-old man was walking along Netherhouse Place and was approached by a man with his dog.
After the assault, the man, who is said to have been in his late 20s, ran off towards Allnach Place.
The victim was taken to the Glasgow Royal Infirmary where he received treatment for a facial injury.
The suspect is described as being white, around 5 feet 10 inches with fair hair.
He is said to have been wearing dark coloured clothing and was walking a medium-sized sandy-coloured dog.
Officers have been carrying out door-to-door inquiries and are reviewing CCTV footage from the area.
Detective Constable John Boyd said: "This man has been walking along the street and has been attacked for no apparent reason.
"I am appealing to local residents and the public for any information which could assist our inquiries.
"Perhaps someone saw the suspect run off, perhaps someone recognises the description of the man and the dog?
"If you have any information or knowledge regarding this crime or the suspect, please contact us."