Tai Samuel Neilson, 25, admitted a charge of assault with intent to injure and yesterday in the Christchurch District Court narrowly avoided jail, with a sentence of five months' home detention.
The attack happened on Shotover St in the early hours of Good Friday this year.
Police told the court Marshall, an 81-test halfback, was pushed to the ground and repeatedly punched, kicked and stomped on. The New Zealand Herald columnist and Sky Sports commentator curled up to protect himself from the blows.
Neilson twice jumped in the air and landed on Marshall with both feet.
Marshall suffered bad bruising to the back, head and body, as well as cuts.
Defence counsel Josh Lucas said Neilson drank alcohol only on "very rare occasions" and that night was one of those.
Neilson's actions were borne out of drunkenness, "bad peer influences and violent tendencies", the lawyer said. He had "out of misguided loyalty tried to help out his friend".
Neilson, who now worked fulltime at a minerals firm, accepted what he did was "disgraceful, idiotic", no matter who the victim was, Mr Lucas said.
Judge Tony Couch said Neilson had an extensive criminal history for serious driving offences, but none for violence.
He was especially concerned Neilson had jumped on Marshall as he lay on the ground, but the judge accepted Neilson had shown "a measure of remorse", and had expressed wishes to have a restorative justice meeting with the former sportsman.
Neilson's co-accused, Adam Kearns, 23, has pleaded not guilty and elected trial by jury in Invercargill.
