As the top Scottish player of his generation, the Glaswegian – who was a Davis Cup team-mate of Andy Murray in the US Open champion's early days – had accrued extensive experience at the top level of the sport. Still only 31 and very much in touch with current practice, he believed he had a great deal to contribute towards the development of the increasing number of promising players emerging in his home country.
"I realise my career did not reach the heights of Murray or [Tim] Henman," Mackin readily acknowledges. "Unfortunately my level of play was not in their class, however I believe I was fortunate enough to have the opportunity to play to a high level and work with some of the best coaches in world tennis during my time practising with Ronald Leitgeb [coach of Thomas Muster] and with Jofre Porta and Joan Bosch [coaches of Carlos Moya]."
Given the environment from which he emerged Mackin had a highly respectable career, recording many wins over players in the world's top 100 level players during his time on the circuit, playing in many high level ATP/Grand Slam events and at one stage even getting the better of an up and coming Rafael Nadal.
However, since Muster and Moya were both world No.1 players who won the French Open, the grand slam tournament which provides the sternest examination of technique and mental strength combined, the knowledge accrued from working in those camps was probably even more valuable. Mackin's view, that he consequently has something close to unique knowhow as an up and coming British coach, seems hard to refute in that context.
It is an opinion that would also now seem to be shared by officials at the Atlantic Tennis Alliance, an organisation formed in Canada little more than a decade ago, among that vast country's eastern provinces.
They offered Mackin a post as one of their technical directors, which he took up two months ago, and while he is very much enjoying the new lifestyle to which he is becoming accustomed – albeit a snow storm interrupted our conversations – there is some frustration at having felt forced into making the reverse journey to that famously undertaken by another of his contemporaries, Greg Rusedski.
"In the UK we do not have a large pool of former players that have played to a high level compared to other more dominant tennis cultures," he points out. "I believe this means we should be doing everything possible to encourage our former players to remain involved in the sport to pass on their experiences to our up and coming players instead of turning them away from the game.
"Unfortunately, things will not change unless the organisation has a clear out and this shall not happen unless the government is allowed to regulate all areas of the organisation."
In saying so Mackin, who is in no doubt that he has been forced into exile from the British tennis scene because he has been prepared to challenge the establishment in the past, has clearly been further emboldened by the recent scrutiny of the Lawn Tennis Association (LTA) at Parliamentary level after Sport England cut its funding.
Some £10.3m of potential support for the sport has been withheld as a result of an astonishing failure to capitalise on Murray's successes of recent years with participation numbers dropping.
That, in turn, prompted an outburst from Baroness Billingham, chair of the All-Party Tennis Group at Westminster, as she took the unusual step of passing direct comment on the £640,000 earned by Roger Draper, the LTA's chief executive which included more than £200,000 in bonuses. "It's unthinkable that someone earning four times more than the Prime Minister has not got ideas for the shake-up of the sport," she said earlier this month.
"This report from Sport England means what the LTA is doing, or failing to do, is absolutely unacceptable. You don't give bonuses for failure, surely and a priority has to be placed on grassroots sport. The LTA is one of the wealthiest sporting organisations in the country and it's my honest and genuine opinion that they are useless. The people who can hire and fire are the board of the LTA, but I see no sign whatsoever that they are moving to even chastise Roger Draper."
It is in that context, and the opinion that vast millions of earnings from Wimbledon have been squandered by the LTA, that Mackin makes his assertion that nothing will change until all is addressed.
"The main problem is that the LTA have no accountability or transparency in the way they are developing, running or growing the sport in Britain," he claims. "They are answerable to nobody and are unregulated. In addition they foster a culture of cronyism. One of the main reasons I decided to relocate abroad is that I simply had no opportunity to contribute or expand my career opportunities at a high performance level in the UK."
In bidding to do so he said he has made direct approaches to Draper himself along with others in the administrative hierarchy of the sport but has largely been ignored.
"Throughout the years I have sent various emails to Roger Draper and various other heads of departments at the LTA offering my services, however 80 percent of the time I am not even afforded the courtesy of a reply. I am now, and have been for a long time, ostracised from the sport in the UK."
It is a sadly familiar tale to those used to dealing with sports administrators in this country, but the fact that Mackin has not been broken by the experience and is now developing his career, offers some hope for the future, even if youngsters on the other side of the Atlantic are set to be the immediate beneficiaries of what he has to offer.