Police are investigating a report that a man in his 50s had his ribs broken in the Donegall Road area, closer to the Sandy Row side of the long south Belfast street, between 1am and 2.10am on Monday.
It was an assault involving three males.
He also sustained injuries to his head and face.
A a 39-year-old man was detained in the area on suspicion of GBH. He has been released pending more enquiries.