Williams (right) in action against Ryan Hogan in June
All Black centre Sonny Bill Williams is to resume his boxing career in January alongside his attempts to secure a place in New Zealand's World Cup squad.
The 25-year-old, who made his debut against England on 6 November, has won his two previous professional bouts.
The fight will take place in Newcastle, Australia on 29 January against Australian Scott Lewis.
"I want to push myself, take myself out of my comfort zone instead of just having a holiday," said Williams.
"I feel that off the field it's doing wonders for me.
"I have to put myself in different situations to get that edge, to keep myself in contention for that All Blacks jersey."
Williams has stopped his previous two opponents, fellow New Zealanders Garry Gurr and Ryan Hogan, in the first round.
He will be trained for the fight against Lewis, a 36-year-old forklift truck driver with a record of three wins and four defeats, by Anthony Mundine.
Mundine, like Williams, began his career in rugby league, before
twice winning the WBA super-middleweight world title.
The contest takes place three weeks before Williams' side Crusaders' opening Super 15 match of the season.
The former rugby league star previously played his club rugby union alongside England World Cup winner Jonny Wilkinson at French side Toulon.
The New Zealand Rugby Union's policy of only selecting domestically-based players for the national side
encouraged him to return home.
The provision within Williams' contract that allowed him to box also strengthened the NZRU's offer in the face of a better-paid deal from Toulon.
"We couldn't compete with Toulon, we were millions and millions apart and this was just one way of securing him," said Neil Sorenson, the NZRU's general manager of professional rugby.
"He's an amazing athlete, he's going to be in a professional environment, he's boxed before and we're happy with the risks."
Reports in New Zealand claim there is provision within his contract to fight again during a break in the Crusaders' playing schedule in either early April or early June.
Ahead of the 2007 World Cup, in which New Zealand were beaten by France in the quarter-finals, the NZRU attracted criticism for withdrawing several stars from club and provincial action.
"There's a risk that he will get injured, absolutely, but it is one that we think is worth taking," Sorenson told Radio NZ.