A 21-year-old New Zealand man gets 13 years in prison for his "colossal" bashing of an Irish man in Sydney's eastern suburbs three years ago.

Kane Tupuolamoui was sentenced in Sydney District Court Thursday on charges of robbery and grievous bodily harm for his role in the bashing of Cork man David Keohane, 29.

Keohane was just about 100m from his Coogee home when he was attacked by Tupuolamoui and another New Zealand-born man, Thomas Isaako, in August 2008. He was left lying on the ground after the two took his wallet and mobile phone.

Keohane, a flooring contractor and Lifeline counselor who had been working in Sydney, was beaten so badly he was in a coma for 31 weeks and is now wheelchair-bound with severe brain injuries.

Judge Ronald Soloman told the court the fact Tupuolamoui had taken ecstasy and alcohol on the night of the bashing did not excuse his behaviour, the ABC reported.

Judge Soloman described the attack as "colossal,'' which left Keohane as "a successful and independent person who now has an uncertain future.''

The judge considered Tupuolamoui's guilty plea but stressed that he had fled to Darwin after the bashing.

Isaako, 20, was sentenced in May last year last year to 19 years in jail with a non-parole period of 14 years for attempted murder over the bashing. He was on bail for an unrelated aggravated robbery when he was arrested.