Former boxer Michael Watson was hurt in a suspected carjacking attempt last week in London, his friend has said.
The 51-year-old, who suffered a near-fatal brain injury in a 1991 fight with Chris Eubank, was in a car with his carer when it was hit from behind.
The carer tried to speak to the driver but was sprayed in the face with “some sort of ammonia”, former boxer Spencer Oliver told BBC Radio 5 live.
Mr Watson was dragged along the road as a man drove off in his car, he said.
Police said both men required hospital treatment, but their injuries were not life-threatening.
Mr Oliver, who spoke to both Mr Watson and his carer, Lennard Ballack, after the incident, said the pair were at traffic lights in Chingford, east London, last Thursday when they got into difficulties.
After a white Mercedes bumped into them, Mr Ballack got out, intending to tell the driver that no damage had been done, Mr Oliver said.
But when he tapped on the car window, the driver leapt out and sprayed him with “some sort of ammonia”, he said.
Mr Ballack fell to the ground and tussled with his attacker, while the passenger tried to hijack Mr Watson’s car, he added.
Mr Watson got caught up in the seatbelt as he tried to get out. As the car was driven off, he was “hanging out of the door”, said Mr Oliver.
The former boxer is now recovering at home from injuries to the skin caused by being dragged along the road.
Mr Oliver said the incident had been traumatic and both men were still shaken up.
The Metropolitan Police said officers were called to the scene shortly before 17:00 GMT after reports of attempted robbery.
A police spokesman said: “Two men, aged in their 50s, informed officers that they had been sprayed in the face with a suspected noxious substance by two suspects who attempted to steal the car.
“The male suspects fled the scene in a different vehicle.
“The victims were assessed at the scene by the London Ambulance Service before being taken to an east London hospital for further treatment – their injuries are not life-threatening.”
Mr Watson’s 1991 WBO super-middleweight title fight with Mr Eubank left him partially disabled and ended his boxing career.
He spent 40 days in a coma and had six brain operations.
In 2003, he completed the London Marathon over six days, defying doctors’ predictions that he would never walk again.