Officers were called at 21:15 to reports two men had approached the victim whilst he was walking along a footpath in Rosebury Park.
They then proceeded to brandish a knife at the man, demanded he hand over his mobile phone and then chased him down West Street.
The first suspect is described as White, has four front teeth missing and tattoos on his neck, and the second was wearing a full grey tracksuit.
Anyone with information is urged to contact police on 101.
