His attackers, 21-year-olds Teira Bennett and Eldea Teuira, both pleaded guilty to two charges in Melbourne Magistrates Court on Wednesday, over the onslaught that left Mokbel with a brain injury and cognitive impairments.

Crown prosecutor Kristie Churchill withdrew two charges, including attempted murder, after the duo agreed to plead guilty to intentionally causing serious injury in circumstances of gross violence in relation to Mokbel, and recklessly causing injury over the stabbing of another inmate, 31-year-old Steven Logan, during the February 11 incident.

Bennett and Teuira were celebrating Bennett's 21st birthday shortly before the incident unfolded.

Court documents reveal Mokbel showed up at the prison-approved party about 2.30pm and handed Bennett a piece of paper.

CCTV footage showed Bennett appearing to read the paper, before briefly embracing Mokbel.

But about an hour later, after Mokbel returned from the prison's visitor centre, he was set upon by the men.

Bennett punched Mokbel to the head. Mokbel had no chance to defend himself and fell backward onto a concrete footpath and appeared to be knocked unconscious.

"Teuira pulls a 'shiv' from his shorts and crouches over Mokbel and appears to be stabbing him in a frenzied motion up to seven times," the prosecution document reveals.

"As this is unfolding, Bennett kicks Mokbel's head three times with apparent force."

Prosecutors said other prisoners, including Logan who was stabbed once, tried to intervene.

Bennett was seen to pull a makeshift weapon from his pants, lift Mokbel and stab him in the upper shoulder area.

"Mokbel does not move from the time of Bennett's first punch and is unable to defend himself throughout the assault," the document says.

Mokbel was airlifted to Royal Melbourne Hospital and underwent an emergency craniotomy to treat injuries including "displacement of brain tissue".

He suffered skull and facial fractures and other injuries medical experts said would have been fatal without swift emergency intervention.

Mokbel was transferred to St Vincent's Hospital where he underwent rehabilitation for cognitive impairments relating to his brain injury, and returned to prison on April 9 after showing signs of improvement.

Prosecutors also revealed prison officials spoke to Mokbel the day before the attack, after a Herald Sun article suggested Mokbel was disrupting a prison extortion racquet run by inmates of Pacific Islander descent.

But court documents reveal Mokbel brushed it off, telling Barwon Prison operations manager Russell Reed during lockdown the article was just someone "out to make money".

A prison officer revealed he heard Bennett yell at Mokbel, "You're not an enforcer, this is what you get for talking to the f***ing screws you dog", during the attack.

"Well done cuz, G-fam," he said to Teuira afterwards.

"Yeah, happy birthday bro," Teuira replied.

Both men are expected to face a County Court plea hearing on October 4.

Australian Associated Press