A witness told a jury he is certain of seeing Manly hooker Manase Fainu plunge a steak knife into the back of his friend outside a Sydney church dance because of one distinctive feature.
"It was the sling," Tony Quach testified in the NSW District Court on Monday.
Fainu, 24, has pleaded not guilty to wounding Faamanu Levi with intent to cause grievous bodily harm at Wattle Grove late at night on October 25, 2019.
Mr Quach said he pushed the footballer and told him to "get out, stop, get out" before he stabbed the youth leader upwards in the back.
Defence barrister Margaret Cunneen SC suggested to the witness that when he heard the mention of a knife, he turned around and ran away seeking help.
But he denied this saying he was "trying to stop everything" before it escalated.
"I just wanted to protect them."
Ms Cunneen suggested he was trying to make himself out to be a hero.
"There is no recognition of being a hero," Mr Quach said.
The men had attended a charity function organised by the Church of the Latter Day Saints when a fight erupted on the dancefloor.
A volunteer security guard told the court he ushered Fainu and his friends outside to the gate but they later returned to the car park and started a brawl.
Prosecutor Emma Curran told the jury Fainu had recently undergone shoulder surgery and had his arm in a sling that evening.
After Mr Levi was stabbed from behind and was later rushed to hospital suffering from internal bleeding and a collapsed lung.
Mr Quach accompanied his friend to the hospital while trying to sort out a sick day from his work as a disability support worker.
"I was just traumatised," he said, adding he was in complete shock.
During the melee the witness said a big guy pulled out a baton and smacked another one of his friends with it.
"That's when everything went crazy," he said.
Mr Quach said it was the first fight he had ever been involved in.
After Mr Levi was stabbed his sole focus was on helping the injured man, but believes the alleged aggressors fled the scene.
Ms Cunneen disputed that Fainu was the stabber, submitting the scene was pitch black, a lot of men were involved and even the victim did not know who wounded him.
The trial continues without one jury member after they contracted COVID-19 last week.