The 26-year-old was on a night out in his home city of Manchester when he was allegedly caught up in a fight.
Footage showed the ex-Manchester United player bleeding from the mouth and lying in the street outside a takeaway.
Some people nearby stopped to help and put him in the recovery position. One is heard saying: "Call the police," while a woman says: "There's blood coming out of his mouth."
At least two people were filming the scene on mobile phones. Another witness can be heard on the film saying: "Someone has just absolutely battered him."
According to reports, he had been punched to the ground, and was later taken to hospital.
The player seemed to back up the story when he tweeted: "For the record im okay, 2 on 1 well done!"
He also sent his bodybuilder father, Peter Samms, a message on Twitter saying: "where was you lol... For the record im okay."
Simpson's profile has been raised since he started dating X Factor judge Tulisa Contostavlos.
Police were not thought to be investigating the 4am incident. Newcastle United did not want to comment.