Guildford, 22, broke team protocol when he hit the town after his team's Bledisloe Cup victory in Auckland on August 6. There was another reported drinking episode at the team's Brisbane hotel after his disappointing on-field performance against Australia later that month.
Laurie Mains said today's players were under much greater pressure than when he played for the team - or when he coached it between 1992 and 1995 - and faced far more relentless media scrutiny.
"In my time as a coach and an All Black getting a few drinks on board wasn't a news-worthy item so the media never used to worry about it.
"Being an All Black in this current environment is extremely stressful and the players need to occasionally let their hair down and relax and enjoy themselves. That will inevitable lead, from time to time, to players perhaps overstepping the line a bit.
"We have to understand the pressure these young men are under and we have to have some tolerance.''
Mains praised the All Blacks' management, and Guildford, for making the issue public rather than waiting for it to emerge in the media.
"They probably nipped it in the bud and, in my opinion, they were smart and they did the right thing.
"I applaud them, personally, for coming out and laying it on the table rather than having some sections of the media go off with a non-factual version of events.''
Mains was confident the young winger would bounce back from the affair and go on to have a successful career.
"Zac Guildford is a very fine young man... and I don't believe that it will (jeopardise his position in the team), just as it didn't with Jimmy Cowan. He will now know the rules and if he doesn't step over the line again he'll be fine. If he does then it might affect his future.''
Yesterday, a sombre Guildford said he felt he let himself and his team down.
"Obviously a poor performance on the field in a week that I felt the pressure at times led to me making a few bad decisions off the field following that game."
Guildford is now on a "self-improvement programme" to address his drinking issues.
"I'm trying to make positive steps and improve as a person and I think that will lead to me being a better player."
The All Blacks are not subject to alcohol restrictions during the World Cup, but are expected to adhere to behaviour protocols.