The 20-year-old victim was walking home after a night out in the early hours of the morning when a group of men in a car shouted 'What are you looking at?' in Walkley Road, Walkley.
He took a detour down Compton Street to try and throw them off but the vehicle appeared moments later round a corner.
Four men got out and started kicking and punching him.
As the victim lay battered and bruised on the ground, the gang stole his mobile phone, car keys and house keys.
A second car containing a man and a woman then pulled up behind and disturbed the gang, who got back in their car and fled the scene.
The good samaritans then took the victim into their car and drove him to safety to a friend's home nearby.
Following the attack, on Saturday, March 30, at 3.15am, the man was taken to Sheffield's Northern General Hospital to be treated for multiple bruises to his face and a bloody nose.
His mum, who did not want to be identified, said: “I got a phone call off his friend saying he had been mugged and I absolutely feared the worst, I was scared to death.
“I went straight round there and we took him to hospital because he was badly bruised and had lost a lot of blood. He was really shaken up by it.”
She fears the gang in the car may have targeted other people in the dead of night and could strike again if they are not caught soon.
She said: “My son went down another street to try and throw them off but it was literally moments later when they appeared so they knew the roads really well. They were obviously just out to cause trouble.”
She added: “I must thank the man and woman who pulled up because had they not it could have been a lot worse, the gang could have continued to attack him.
“We have made contact with them since to thank them.”
She described the vehicle as a silver “family style car, possibly a Toyota” and added the four attackers were “Asian or mixed race” men aged in their early to mid 20s.
They reported the incident to South Yorkshire Police.
In a statement, the force said: “No arrests have been made at this stage.
“Did you witness what happened? Did you assist the man?
“If you have any information that could help, please call 101 quoting incident number 154 of 30 March 2019.”