Haiu's lawyer Richard Earwaker said his client had received the news he had cancer, one month before the assault. The cancer meant he could not play rugby in Japan.
"That, in effect, was his security blanket."
He said Haiu had lost between $400,000 and $500,000 in property deals with Mr Cooper and had tried to contact Mr Cooper without success.
"He had concern for his family."
Mr Earwaker said a conviction would be out of all proportion to the gravity of the assault.
He said Haiu was now focussing on his health and was waiting to see the results of further tests.
"It is still too soon but it seems the tumour has decreased in size but it is still far too early to tell."
Mr Earwaker said Haiu would be willing to do some form of voluntary community service.
Police did not oppose the application but prosecutor Geoffrey Bardsley said Mr Cooper wanted some form of punishment.
"He indicated he did not wish to stand in the way of the defendant's career and overseas travel."
Judge Gerard Winter has reserved his decision and Haiu is due back in court next month.
The Auckland lock, who has played 53 games for the Blues and 75 for his provincial team, was diagnosed with bone cancer in April and has been on indefinite leave from rugby.
