The middle-aged man shook with rage at the suggestion that his son had been involved in gang violence.
Raffles Institution (RI) student Anand Ravindran, 17, was stabbed on Thursday. A witness had suggested that it was like a gang fight.
But Anand's father, who was with him at the hospital yesterday, insisted that the teen was just a victim.
Police have arrested five youths in connection with the attack, which took place just before 4pm at Potong Pasir Avenue 1.
The New Paper reported yesterday that Anand, a first-year A-level student at RI, was seriously injured when he was stabbed in the back by a group of youths.
A trail of Anand's bloody footprints led from where he was stabbed to a clinic nearby, where he collapsed while trying to get help.
Minutes before the attack, Anand, his friend, Don Tan, also 17, and two other teenagers were seen by a man at a coffee shop, talking about "organising a fight".
They were said to have been involved in a staring incident a few hours earlier.
But Anand's father flew into a rage when asked about this. The tall, well-built man in office wear, who declined to be named, said: "It has already been established that my son was a victim."
He raised his voice and continued: "Do you know what it's like to have almost lost a loved one? My son could have died."
He refused to say more.
Anand was in a high-dependency ward at Tan Tock Seng Hospital.
TNP understands that his teachers from RI visited him last evening.
Various tubes were connected to his body, but he could sit up in bed.
Don, Anand's ex-schoolmate who recently finished his O-level examinations at Saint Andrew's Secondary School, had suffered a bruised right eye from the attack.
Don said he visited Anand in the hospital with a group of friends yesterday afternoon.
"Anand is okay now," he said. "He's conscious. He recognised us and he even talked a little."
Don's mother, who gave her name only as Madam Tang, told TNP in Mandarin that she was worried for her son's safety.
She said: "I keep thinking...what if other youths come back to attack him?"
Madam Tang, who is in her 40s, said she had advised Don not to leave the house and concentrate on recovering from his injuries.
She said she was worried for Anand, too, and had tried to visit him on Thursday night, when Don was being treated at the same hospital, but visiting hours were over.