Louie Sibley posted on Twitter on Sunday evening to say his partner Keeley Carter was left needing stitches after being "attacked several times by a man and a woman".
The young midfielder shared a photo of the bloodied victim and said the man had "knocked her out" after he "dragged her to the ground".
He added that his girlfriend had also been "slammed up the wall".
On Tuesday, Nottinghamshire Police posted two CCTV images of four people they are tracing after Sibley reported the assault.
In the appeal shared by footballer, the force said the victim was assaulted in Upper Parliament Street at 2.08am on Sunday.
Chief Inspector Amy English, of Nottinghamshire Police, said: "This was a nasty assault which left the victim needing hospital treatment.
"We have been trawling through all of the CCTV footage available from the night as part of our investigations, to help establish what happened.
"After reviewing the footage in detail, we have identified four people who we believe may have information that could help our inquiry and I urge them to come forward.
"Anyone who witnessed the incident, or recognises anyone in the images, is also asked to call us on 101, quoting incident 86 of 12 June 2022, or call Crimestoppers anonymously on 0800 555 111."