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It comes in the wake of another alcohol-related issue, when he allegedly assaulted a partygoer at a Christchurch house on January 12 after a drinking and gambling session.
Guildford, who has played 10 tests for the All Blacks, has been involved in a string of high-profile incidents over the past 18 months, including a drunken rampage in Rarotonga in November 2011 that resulted in his arrest. He ran naked and bleeding into a bar before assaulting two patrons
After that incident, the Napier-born player admitted he was struggling with a drinking problem and vowed to give up alcohol for 12 months.
He has gone into hiding since allegations of the latest incident emerged this week but has withdrawn from the Crusaders to seek treatment.
"We are all supporting Zac and see this as a positive step forward in overcoming his illness," Crusaders coach Todd Blackadder said. "This is ultimately about his well-being so it is important for him to take the time to fully address it.
"We are unclear on what it means for the Crusaders at this time."
Blackadder had earlier said Crusaders management were considering whether Guildford would be dropped from the franchise for the rest of the season.
The NZRU banned Guildford for four matches after his post-World Cup exploits in Rarotonga in 2011. He missed the Crusaders' round one fixture against the Blues last season, with the rest of the suspension served during the pre-season campaign.
"It has been a challenging week for everyone involved, and we are working closely with the players' association and his manager to ensure that he gets the professional help he needs and is held accountable for his actions," NZRU chief executive Steve Tew said. "As people may appreciate, this is an employment matter and we must ensure that the process both respects his right to a fair hearing and our legal obligations as an employer.
"We also have a responsibility to the wider game and all those who support it. We are working hard to deliver on our obligations to the game.
"Zac's withdrawal from the Crusaders means they are able to concentrate on preparing for their 2013 season, and Zac will be free from rugby to concentrate on resolving his personal issues. We will remain in touch with Zac to monitor his progress and will address the issue of misconduct at the appropriate time."
The NZRU are likely to take a dim view of Guildford's latest indiscretion.
"Zac has a renewed acceptance of the challenges he faces," New Zealand Rugby Players Association chief executive Rob Nichol said.
"We have taken the advice of experts and Zac is committed to the plan they have developed. It is fundamental that he commits fully to the plan, and sees it through. This means withdrawing from the rugby environment.
"We are all supporting Zac during what will be a challenging time. Zac himself wants to make the most of the opportunity provided and is very appreciative of the support he is receiving."
The Zac Guildford file
Broke team rules when he left the All Blacks' hotel to go out after their Bledisloe Cup victory against Australia at Eden Park. Within weeks, he drank heavily and broke the team curfew after the All Blacks' 25-20 defeat to the Wallabies.
Guildford admitted to having issues with alcohol and promised he would get problem under control.
The 23-year-old was arrested after he stormed into Trader Jacks in Rarotonga naked and allegedly punched two men. He then announced a self-imposed 12-month drinking ban, saying: "I need to sort myself out."
After being photographed drinking at a function, Guildford said he had changed his ways and now trusted himself to enjoy one or two drinks with friends.