Wellington rugby player Losi Filipo has been sentenced to nine months' supervision after pleading guilty to assaulting four people in Wellington in 2015.
The nine-month sentence is for the attack on the main victim, Greg Morgan. Filipo was also sentenced to six months' supervision for the other three offences, to be served concurrently.
He has been ordered to undergo counselling.
High Court Justice David Collins said that stomping on the head of an unconscious victim was a "chilling offence".
Filipo's lawyer Noel Sainsbury acknowledged the seriousness of the offending but said he wanted the sentence to ensure rehabilitation would be possible.
He cited Filipo's disadvantaged background, his future potential, the fact that he had done community service and paid reparations.
Mr Sainsbury referred to Filipo as "a young man with incredible promise, a young man that's struggling with a number of difficulties".
He asked the judge to take into account the fact Filipo won't have the opportunity to play rugby in Japan or the United Kingdom, and that he had lost his Wellington Lions rugby contract.
He hadn't offended for a year and was undertaking counselling.
Mr Sainsbury also cited a Facebook post that Mr Morgan wrote in May of this year, announcing he was giving up rugby.
Mr Morgan says the head injuries inflicted by Filipo ended his promising rugby career.
However, in the Facebook post he says his decision to retire was due to suffering 15 concussions since 2011, four of them over the past four months.
Mr Morgan in hospital after the attack (supplied)
"Should've stopped ten concussions ago," Mr Morgan wrote in the post. "Choosing to toughen up and carry on with the game I love has now taken effect on me today."
"I'm only 20 years old. If I were to receive another concussion the consequences are unthinkable."
Filipo had originally been discharged without conviction for the attack, but police appealed the decision.