The 32-year-old revealed the lingering effects of concussion were so bad he had to be held up at the altar at twin brother and fellow ex-Wallaby Saia's wedding due to a head injury

"In 2016, my twin brother got married and at the altar, I was actually getting held up because of the head knocks," Fainga'a told Fox Sports News.

Fainga'a has been playing in Japan for the past three seasons but was concerned about the affects of another hit.

"I'm probably only one more head knock away from being a vegetable or not being able to play with my kids," Fainga'a said.

"I got a few head knocks last year and after all these head knocks I had to make a decision, make a choice about what I wanted to do with my future.

"I love the rugby game so much but I needed to look after my mental health."

Fainga'a played 23 Tests with the Wallabies and was a member of the Reds' Super Rugby championship-winning team in 2011.

He plans to move back home to Brisbane with his family.

Australian Associated Press