The 17-year-old boy was punched to the face and fell to the ground before a soccer ball-style kick was delivered directly to his head.

He managed to walk to a friend's house where he began vomiting and felt dizzy. When the teenager went home, his mother drove him to the closest hospital.

He was then airlifted to the Royal Melbourne Hospital with a fractured skull, cheekbone and eye socket, and bleeding on the brain behind the fracture. He has since undertaken extensive rehabilitation.

Jayden Stanley Blomley, of Delacombe, Brody Harrison Burke, of Cape Clear, and Bon Dylan Pails, of Delacombe, were charged over the fight.

Burke, 21, and Pails, 23, pleaded guilty on Thursday to two counts of intentionally causing injury following a two year delay of the case resolving. Blomely, 22, is facing a trial in the County Court at a date to be fixed.

Crown prosecutor Fraser Cameron told the Ballarat Magistrates' Court the three men were visiting Warrnambool on January 20, 2018, and had attended licensed venues during the night.

He said the victim and two teenage friends, who were unknown to the Ballarat men, had attended a fundraising table tennis tournament and left the venue after 12.30am on January 21.

As the group of friends approached the intersection of Banyan and Cramer streets about 12.55am, Blomely and Burke allegedly came out from behind bushes, stood in front of the victim's friend, aged 17, and a verbal altercation occurred.

"The offender Burke stood in front of (the victim's friend ) and in a head-butting motion, Burke used his forehead to strike (him) to the mouth. This resulted in a laceration to his lip," Mr Cameron said.

"(The victim's friend) immediately stumbled backwards onto the roadway."

Mr Cameron said the victim initially stood away from this fracas but Burke approached him, stood in front of him and struck him to his face with his hands.

"(The victim) went to the ground however Burke continued to strike (him) and as this was occurring, Pails ran along the footpath on Cramer Street directly at (him) and kicked him directly in the head, soccer ball-style," he said.

Mr Cameron said the teenager immediately felt pain when he was first struck and his right eye swelled up. A CT scan at a Warrnambool hospital showed the head injuries and he was airlifted to the Royal Melbourne Hospital.

"When reviewed in November, 2018, (the teenager) was still suffering a number of medical complaints arising from the assault, including anxiety attacks, shortness of temper, headaches, poor sleep and poor concentration," Mr Cameron said.

"On balance, he appeared to be suffering from post-concussion syndrome amd post-traumatic stress disorder."

Through a statement read to the court, the victim - now aged 20 - said he knew he would never be the same person as he was before the incident.

He said he was not expecting to be attacked and he remembered "feeling like I wasn't in control of my body" and "I couldn't see anything and I wondered if I would lose my eyesight".

The victim said he became mad and frustrated easily.

"I get triggered easily ... I have no tolerance anymore. My anger erupts. I know I will never be the same person and I was before the incident," he said.

The victim's mother, who was in court, described through her statement how hard it was for her to see her son return home battered and bruised.

She said when her son was put in the Ambulance Victoria helicopter, all she could say to him was 'you will be OK'. The victim could not play sport for six months and missed a cricket grand final, he missed days at school and stopped his usual socialising.

The victim's friend received a cut to his left upper lip that required suturing, while a female teenager had redness and pain in her chest from allegedly being pushed.

Defence lawyer Andrian Paull, representing Pails, said during the fight his client had been vomiting in the bushes because he was drunk. He said Pails' involvement lasted six to seven seconds when he kicked the victim while he lay on the ground.

"This is something that appears to happen spontaneously without any thought. It was completely out of character," Mr Paull said.

"He has gone about his life as a law-abiding citizen since this ugly incident."

Mr Paull said Pails had written letter of apology to the victim. He submitted a fine or a community correction order was within the sentencing range.

"He would be vulnerable if placed in a prison environment," Mr Paull said.

Defence lawyer Andrew Madden, representing Burke, said his client's involvement included headbutting the victim's friend before striking the victim and it was unclear if he or Pails caused the victim's serious head injury, saying they were jointly liable.

He said alcohol was the main factor behind the incident and they had not intended to become involved a fight on the night.

Mr Madden said Burke wanted to express his remorse to the victim and his family. He urged the court not jail Burke, who was working to become an agricultural contractor.

Police obtained security camera footage of the fight from a neighbour, which led to the men being identified as they had been to Warrnambool licensed premises before the incident.

Burke and Pails were arrested on January 29, 2018.

On Thursday, pair's bail conditions were extended and they were directed to reappear at the Ballarat Magistrates Court on July 10 for sentencing.

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