The 28-year-old man was found in the car park of the Crown Hotel pub at around 11.45pm on Sunday June 28.
He had a broken jaw and a head injury, and spent several days in hospital. He is still receiving treatment for his injuries.
Initially, police were led to police the man had fallen, but new information has come to light to suggest otherwise.
Despite repeated efforts to speak to people at the scene who may have seen what happened, no witnesses were found, and police have re-appealed for people to come forward.
A South Yorkshire Police spokesman said: “We’ve worked hard to find anyone who might have been able to shed light on how the man came to be injured, but information has not been forthcoming.
“We’ve recently received new information to suggest the man had been assaulted. It’s still unclear how he came to be injured and I’d like to appeal to anyone who knows what happened to please come forward.
“The victim continues to have issues as a result of his injuries and we’re determined to achieve justice for him.”
Police want anyone who was at the pub that night or saw what happened to contact them on 101, quoting incident 1484 of 28 June 2015, or email [email protected]