Mr Gallaway, a partner at Chapman Tripp, has acted on behalf of a number of high-profile athletes, including one with a serious alcohol problem who he said with strong support systems was able to get through his playing career successfully.
Despite being team games, sports such as cricket and rugby could be incredibly lonely, Mr Gallaway said.
"You are surrounded by a culture that celebrates milestones with alcohol, when you have one athlete in that environment who doesn't drink, it's very isolating."
He believed Guildford had a very serious problem, and one that had not been recognised by the player.
"When he takes himself off a self-imposed ban two months early, and said he felt able to have a social beer with his friends ... I mean there's a phrase 'you can't be half-pregnant'. And you can't be half an alcoholic; you've either got the problem or you haven't."
Mr Gallaway said opinions expressed on radio yesterday showed much of the sporting public did not understand the issue.
"You will hear people ringing up and saying ... 'Guildford has proved that he's just human'. He hasn't at all. He's proved that he's got a massive problem and it's ongoing."
Roger Green of The New Zealand Retreat, a rehab centre for alcoholics, said that with proper treatment and support Guildford could bounce back. Mr Green, 75, was an All Black triallist at 19 and a junior team member, but his career was effectively ended by alcoholism.
He said he believed Guildford should have been advised to give up alcohol completely.
Both men said there was great opportunity in the possibility of the winger's eventual rehabilitation.
"He has a really wonderful opportunity to be a role model for people with similar problems," Mr Gallaway said.
Read more: Guildford 'out of control' at party