This year Matt and Lucas Cronin kept a place unfilled, as if their son and brother Patrick still sat between them, yelling for the Tigers he loved.

But he hasn't been.

Patrick Cronin, 19, suffered fatal head injuries when punched to the side of the head by Andrew Lee during a brawl at the Windy Mile hotel in Diamond Creek on the night of April 16 last year.

At his funeral, Mr Cronin was remembered as a young man who could talk endlessly about Richmond Football Club. It's a passion his family still share.

In the Supreme Court on Tuesday they spoke of the bittersweet feeling that accompanied the club's AFL premiership win on Saturday.

The teenager's mother, Robyn, said she cried whether they won or lost.

Matt Cronin, wearing a Richmond lanyard, told the court he and Lucas now keep a spare seat between them when they watch the Tigers.

Mr Cronin also read a statement he wrote from Patrick's perspective, in which the teenager squeezed his parents' hands as his life began slipping away.

"I still don't know why I was hit because I wasn't a threat to anyone. I just weigh 72 kilos and I look about 15," the father said, before tearfully concluding: "My name's Pat. I am 19 years old and I always will be."

Lee, 34, pleaded guilty to manslaughter last month, days after his trial on that charge began.

He had initially been charged with murder but the more serious charge was withdrawn by prosecutors earlier this year.

Mr Cronin was punched without him seeing Lee, as the teenager tried to drag a friend out of the brawl.

He left the pub with friends and fell ill within hours and died in hospital the next day.

About 100 people packed into the Supreme Court on Tuesday for Lee's pre-sentence hearing, when Mr Cronin's parents and siblings, Emma and Lucas, tearfully read statements to express the heartache of losing the cheeky, friendly, caring and youngest member of their family, who was a promising footballer for Lower Plenty and an aspiring physiotherapist.

They also slammed Lee for his actions that night, his long refusal to accept responsibility and the hatred they now felt.

"It all could have been avoided if one person had decided not to throw a punch, a cowardly punch," Matt Cronin said from the witness stand, looking directly at Lee.

Ms Cronin said her world felt "wrong" without her son, and that her constant sadness brought tears every day, and left her in a "deep dark hole that feels inescapable".

Her grief was harder, she said, because of the protection the law had given Lee, who was twice granted bail over the past 17 months, once even on the day he pleaded guilty.

"I never had anger and hate in my heart," Ms Cronin said.

"I am a good person and I don't want to feel this way but how can I ever forgive this?"

Another 89 victim impact statements were passed onto Justice Lex Lasry but not read aloud, before the Cronins and many of their supporters walked out of the court when defence counsel Peter Morrissey, SC, began his plea submissions. They returned in the afternoon.

CCTV footage played to the court showed Mr Cronin trying to get friend Anthony Hopkins out of the brawl, before Lee stepped in from the side and punched both men, before fighting with others.

Prosecutor Brendan Kissane, QC, said Lee was proficient in Muay Thai, a form of martial arts, and the force of his strike knocked Mr Cronin's head back.

But Mr Morrissey said his client never intended to punch Mr Cronin in "the scene of chaos", and was instead aiming at Mr Hopkins, who had traded punches with Lee's friend, Aaron Burns.

Prosecutors initially applied for Justice Lasry to impose a mandatory 10-year minimum jail term under Victoria's 2014 one-punch laws, but withdrew the request when they couldn't prove Lee intended to punch Mr Cronin.

Mr Morrissey said Lee was "a good person who did a bad thing" and sought forgiveness from the Cronin family in a letter of apology. Matt Cronin shook his head as the letter was read out.

Lee, a father of a two-year-old boy and supported in court by about 30 people, was remanded in custody to be sentenced in November.