The 51-year-old driver was punched then kicked on the arm after turning his cab around to return a mobile phone to the man, who had left it in the back of the car.
The attack happened at 8.30 pm near the Caesarean Tennis Club when the driver dropped the passenger off.
He had picked up the man outside the Don pub, and described him as having a Scottish accent, 5ft 9 and heavily built, with short brown hair.
The man was wearing a white short-sleeved Celtic football shirt, short trousers and trainers and was asked to get out of the taxi after being sick.
Police said the driver stopped the car and told him to get out, at which point the man paid the fare.
But after driving off, the taxi driver realised the man had left a mobile phone on the seat, so stopped to return it, when the attack happened.