A boxing coach is facing jail for leaving a rival nursing a fractured skull during an Old Firm Day fight.
Scott Gethins punched Derek Robertson, knocking him out and sending him crashing to the floor.
Robertson's head hit the ground so hard a witness said it sounded "like a really old waterlogged football".
Blood began to pour from Robertson's ear as he lay unconscious and motionless on the ground.
And when he was rushed to hospital after the attack, medics discovered his skull was fractured and he had bruising on the brain.
Robertson was also left deaf in his left ear due to the injuries he sustained in the attack, which took place in Renfrew, near Glasgow.
Gethins, 54, admitted hitting Robertson on the day in question - March 31, 2019 - hours after Celtic had beaten Rangers in a Scottish Premiership clash at Celtic Park.
But he denied assaulting Robertson and his wife, Lesley Ann Robertson, claiming he lashed out in self-defence after being attacked and abused by the couple.
He told his Paisley Sheriff Court trial he was branded 'a F****n' by Mrs Robertson, who also made comments about people "not coming from Renfrew".
He said he was kicked and punched by her after having the sectarian slur thrown at him, and said Mr Robertson punched him in the face before he lifted his hands.
He claimed he punched Mr Robertson once and pushed Mrs Robertson once, in self-defence, causing them both to end up on the ground.
And he told the court that he is a boxing coach who teaches kids from the age of seven and knows how to throw a punch.
BBC Scotland journalist Mike Farrell, who works as a reporter with the broadcaster, said he saw the attack while going to buy beer after the game.
He said he was so worried about what he'd witnessed he feared the man may die, so immediately called 999.
And he said he was so shaken up by what he'd seen he couldn't drink any of the beers when he got home.
The 33-year-old said: "Celtic and Rangers had been playing earlier in the day.
"I had been at home with my wife and son, who was nine or ten months old at the time.
"At night I went out to the shops."
He said he saw Gethins punching Robertson in the face - and knocking him out.
He explained: "You could tell instantly that the man was unconscious - he was out cold before he hit the floor.
"When his head hit the pavement it sounded really kinda dull and wet, like a really old waterlogged football kinda thud on the ground.
"I thought, 'this guy could be a goner'. I thought, 'this guy could be dead'. Blood started coming out of one of his ears.
"I had my phone out and was dialling 999. There was a pool of blood coming out of his ear on the floor.
"I was going to the shop to get some beers and I remember, by the time I got home, I didn't have any - I was that shaken up by it."
On Monday, the jury convicted Gethins, of Renfrew, of both charges - assaulting Mr Robertson to his severe injury and permanent impairment by punching him on the head, causing him to fall to the ground, and assaulting Mr Robertson, to her severe injury, by punching her on the head, causing her to fall to the ground.
Sheriff Bruce Erroch QC called for background reports to be prepared ahead of sentencing, adjourned the case until next month and continued Gethins' bail.
Celtic won the match in question 2-1, thanks to goals from Odsonne Edouard and James Forrest, in a game which saw Ryan Kent score for Rangers and Alfredo Morelos and Andy Halliday sent off.
