Andrew Anastasi, 59, was walking back into a pub when a man surprised him with a heavy blow to the side of his face on December 22.
The teetotaller suffered a fractured cheekbone, four fractures to his eye socket, bleeding on the brain and concussion.
He has spent Christmas on painkillers being cared for at home by his wife Mary-Anne, 47, and will have surgery on his cheekbone and eye socket tomorrow (31/12).
Mr Anastasi, a self-employed engineer who lives in Alvaston, Derby, was out having drinks with clients at the Howard pub on Howard Street in Sheffield when he went out for a cigarette.
When he returned to the pub, he was viciously attacked.
Mary-Anne, a training assessor, received a call at 10.30pm from a paramedic, who said Mr Anastasi had been punched.
The father-of-three and grandfather-of-one now feels scared to go out again.
Mary-Anne said: “Andrew can’t really talk at the moment.
“He is waiting for surgery on Monday.
“He had a smashed eye-socket in four places and a smashed cheekbone.
“We were back in hospital on Christmas Day. He received a bleed on the brain from it.
“He was very ill on Christmas Day. He had severe concussion.
“On December 22, Andrew went to Sheffield.
“He was at the Howard Pub with some clients.
“They went for a meal at Frankie and Benny’s beforehand.
“At about 10.30pm I received a call from the ambulance man - I was extremely shocked.
“Nobody would believe Andrew would ever get into a fight.
“He doesn’t drink, he’s never had a fight, he’s never picked on anybody.
“His only vice is cigarettes.
“When he walked back inside, he was attacked without provocation.
“It was a single punch.
“I think he collapsed - he’s not 100 per cent sure.
“I’m sure he would have blacked out for a second or two.
“I was like ‘what?’. I couldn’t believe it.
“I thought it could have been because he has recently got a shaved head, but it wasn’t that.
“I am worried because tomorrow is New Year’s Eve, and this person is a danger to people.
“If another attack happens, it’s just awful because he should be locked up, awaiting whatever the judge decides to do with him.
“Andrew is really, really good with pain.
“Fifteen years ago, he had an industrial accident so this is not the first time something extremely serious has happened to him.
“He thinks he would be a bit scared to go out now.
“He is angry, but I don’t think he has reached the full extent of that yet.
“More than anything, we want to know why. Why would you do this?”
South Yorkshire Police said two men were “seriously assaulted” by an “unknown man” at the Howard pub in Sheffield.
Officers released four pictures of a man they believe could hold "vital information" about the incident.No one has yet been arrested.
“At around 9.45pm on Saturday 22 December, it is reported that two men were seriously assaulted by an unknown man at the Howard pub, on Howard Street in Sheffield.
“It is understood that one of the victims was assaulted inside the pub, while the other was assaulted as the suspect left the pub.
“The victims, men aged 59 and 57-years-old, both suffered serious facial injuries that have been described as life altering. Both men required hospital treatment for their injuries.
“Officers believe the man pictured holds information that could help the investigation and want to hear from him, or anyone who may recognise him.
“Please call 101 quoting incident number 987 of 22 December 2018. You can also ring Crimestoppers anonymously on 0800 555 111.”