It is 51 years since Cardiff were in the top flight, and the wait has intensified the reaction since his team won the Championship last season.
By March, supporters in south Wales were already anticipating the prospect of the derby between Cardiff and Swansea City. These two clubs have forged their own paths, but they are now in the same place. From the brink of collapse, Swansea relied on a sustainable plan, one that combined a contemporary football philosophy with an ownership structure that has renewed the influence and so engagement of their fans. It has taken Tan, a Malaysian billionaire, to free Cardiff from restrictive debt but also the psychological agony of a series of dramatic promotion failures.
Since earning a place in the Barclay's Premier League, Tan has settled a £24m debt and pledged to donate £1m to local charities in each of the seasons that he remains majority shareholder and Cardiff stay in the top flight. This follows a £10m investment in the training ground and the expansion of the stadium. He has rebranded the club, changing the colours from blue to red, but there was little dissension from supporters when progress was finally being made.
Mackay has benefitted from the support - both financial and in terms of ambition - but he has also made the most of it. For all that Craig Bellamy is an iconic figure, and players such as Mark Hudson, Kevin McNaughton, David Marshall and Peter Whittingham have proved their effectiveness in a reassuring period of commitment, Mackay has facilitated Cardiff's rise. Tan backed his manager's judgement, with the club's transfer record being broken three times this summer, following the signings of the Danish striker Andreas Cornelius for £7.5m, the centre-back Steven Caulker for £9m and the combative midfielder Gary Medel for £9.5m. The upgrading was vital, but Mackay is adamant that the principles underlying his management must remain intact.
"We could have bought quantity, but I already had quality," Mackay said. "This group won the league by eight points and were top from November onwards. Only three teams have done that in 10 years. This group deserve to be there. The players I brought in had to be higher quality and improve the club.
"What we've built on is just the next phase. When I came here, I spoke to the directors about my plans and the strategies I wanted to put in place. That was building a recruitment department, a sports science department, an academy, changing the medical department and the coaching structure. That just means we're at the next level up and everybody improves their aspect of the club. It's about tweaking things and keeping our standards high. We have good people and they're being allowed to go to the next level of their job."
The surrounding commotion is an additional pressure for Mackay to manage. He is unaffected, even if his profile is now that of one of the leading young managers in England. It is 15 years since he moved south, a passage of time that has taken him by surprise. He still maintains contact with Scottish football, though his father, Malky senior, who is on the board at Queen's Park, and Jim Fleeting, the Scottish Football Association's director of football, but Mackay is following the standards set by fellow Scots who have established themselves as managerial talents in England.
He counts many of them as sources of advice. Mackay is clear about his style, but is still prepared to seek other opinions. During the summer, he spoke to 10 managers who have worked in the Premier League, six of whom took teams up from the Championship. Three of those then lost their jobs, but the precariousness of the work cannot be allowed to be inhibiting.
"You want to test yourself at the highest level," Mackay said. "I'm looking forward to doing that. I'm under no illusions about how tough it will be. I've spoken to people who have managed in the league in the last couple of years, guys I know well. There were obvious things but also little pointers and little pieces of advice. It's about how we approach things but I'm always looking to speak to people who have been there and done it."
His first match is at Upton Park today, which was also the ground where he managed Cardiff for the first time. It took two years to guide the club out of the npower Championship, but the sense is that Cardiff are better prepared for that journey, and the set-up it allowed Mackay to implement. He also won that first game, which he hopes will be a lucky omen. In truth, though, it is preparation and intelligence that he is counting on.
"For the last two years things have been on the up in Wales in general, particularly in sport," Mackay said. "There's been Wales in the Six Nations, the paralympians, Nathan Cleverly, ourselves, Swansea, Newport and Wrexham in the football. We're very keen to keep fostering that. It's a lovely city and a passionate place to watch football."
Under Mackay's guidance, Cardiff could also become established in the Premier League. That, for now, is his aim.