Paul Gallen's upcoming fight will be the 20th professional bout of his boxing career, against former Melbourne Storm forward Nelson Asofa-Solomona, who is 15 years younger.
The 45-year-old NRL premiership winner is returning from retirement for the heavyweight contest in Sydney on Friday week, 16 months after beating Sonny Bill Williams by split decision.
Gallen told AAP his wife opposes the fight, but supporting his family is his main reason for taking it.
"Nah, she's not happy. She's not happy at all," Gallen told AAP about his wife's thoughts on the fight. "But it's my job as a bloke. It's my role in the relationship. I provide for my family.
"I'm going to give my family a life I never had and that's my sole motivation. That's what I'm here for: to look after them and that's what I'm going to do."
Gallen said he also wants to settle a score with Asofa-Solomona, whom he helped get started in boxing through No Limit Boxing.
He said Asofa-Solomona kept calling him out after he had retired, and added: "I told him I was done. I told him I was finished," Gallen said. "He wasn't calling out Curtis Scott. He's not calling out Junior Paulo. They're footy players. They're younger. I'm 45. He keeps bringing up my name after the fact because he knows I didn't want to do this anymore. I'm going to smash his face in."
After a 19-year NRL career, Gallen said he had undergone brain scans and consulted medical specialists before agreeing to fight again.
"I've done everything I can to ensure I'm in a good spot," he said. "People talk about CTE. I've heard former footy players talk about it. But you do not know you've got CTE until you're dead.
"I've been tested, I've been scanned. There's no way a doctor's going to say, 'yeah, you can still fight'. I've been told I'm in a good spot and after this fight I'll get tested again."