A worker at Asda in Longwell Green was taken to hospital after being attacked by a man.
It was one of two assaults on staff which took place at the store on July 19 at 1.05pm.
The worker taken to hospital has since been discharged.
Police investigating have looked over CCTV and have released an image of a man, pictured, they wish to speak to.
He is described as being about 20 years old.
Witnesses, or anyone who recognises the man we want to speak with, should call 101 and quote reference number 5222174818.