Jonah Lomu is disappointed he can't take part in the Fight for Life fundraiser.
The event is taking place on December 3 at Trusts Stadium in West Auckland.
Six rugby players will fight six rugby league players in three two-minute boxing rounds.
Lomu says he trained hard to get into shape and be fighting fit, however, he says at the end of the day, you can't control your health, and when it decides to pack up you can't do anything about it, apart from trying to get it under control.
He says another day above ground is always a good one.