Tuau and two friends gave chase and cornered Mr Bryden alone on Tory St.
He punched Mr Bryden to the ground before repeatedly kicking and stomping on his head against a concrete barrier.
The attack continued after Mr Bryden lost consciousness and stopped only when a member of the public intervened.
Mr Bryden was taken to hospital in a critical condition and was on a ventilator for a number of days. He was expected to remain in a brain injury rehabilitation unit for one to two years.
Tuau handed himself in five days after the assault, telling police he did not recall what happened as he had been drinking heavily and had blacked out just prior to the incident.
In the High Court at Wellington today, Justice Forrest Miller sentenced Tuau to nine years, with a minimum non-parole period of four-and-a-half years.
Tuau played league for the Penrith Panthers in Australia's under 20-competition for two years before joining the Te Aroha Eels in Lower Hutt in 2011.