Aaron Smith was handed a one-game suspension and faces a misconduct hearing after members of the public spotted him following a woman into a disabled toilet last month, while he and his All Blacks teammates were waiting at Christchurch airport.
"I've made a huge mistake, a huge error in judgment," the 27-year-old told reporters at the team's hotel in South Africa Thursday.
"I'd firstly like to say a huge sorry to my partner Teagan, her family, my family. I'm also sorry to my teammates, NZRU and the New Zealand fans.
"My behavior was unacceptable. I'm just trying to get home to deal with this. Thank you."
In a country where rugby is the national sport, players are seen as role models -- but this incident is just the latest in which the game has made headlines for the wrong reasons.
It took place on September 18, the day after New Zealand beat South Africa 41-13 in Christchurch. Smith, wearing official team uniform, was seen following the woman into the toilet by a family waiting to use the cubicle, and then emerging separately 10 minutes later.
"Most people would not do that, let alone a public figure," one of the witnesses told New Zealand website Stuff
. "They are kings and treated like absolute royalty -- we hold these people so high in regard."
New Zealand's prime minister John Key said Smith had "embarrassed himself."
"I think the rugby union, coming off the back of a couple of other pretty poor PR issues in recent times, will want to make sure they send a strong message to the All Blacks that they have a high level of expectation in their behavior," Key told New Zealand media outlets.
All Blacks coach Steve Hansen said Wednesday the team's leadership group had imposed the one-game suspension, which means he will miss Saturday's Rugby Championship game against the Springboks. The world champions will be seeking to equal the record of 17 consecutive international victories
by a top-level country.
Hansen said Smith, who was not selected for New Zealand's October 1 game in Argentina, had asked to return home from South Africa.
"We are taking action to improve the culture of our game and are about to embark on an independent review of respect and responsibility in our professional player environment," its chief executive Steve Tew said in a statement.
The controversy has upset the All Blacks' preparations for their bid to equal the milestone set by their predecessors in 1969 and 2014, and South Africa in 1998. New Zealand also had a chance to win 17 in a row in 2012, but drew with arch-rival Australia.
Hansen's team has already wrapped up the Rugby Championship title ahead of the sixth and final round, but will have a chance to set a new record if it wins Saturday and then in the Bledisloe Cup clash with the Wallabies in Auckland on October 22.
The Springboks ended New Zealand's 17-match run in 1970, and current coach Allister Coetzee wants his team to build on last weekend's 18-10 win at home to Australia.
"We are playing at home and the boys are looking forward to the encounter against the world's best team," he said.
Smith made his New Zealand debut in June 2012 and has passed a half-century of international appearances, being part of the 2015 World Cup-winning side.