McKay, who previously served as the chief executive officer for Scottish Rugby Union, was announced as Peter Lawwell’s replacement at Celtic in late January.
Taking over such a role at a time when Celtic, who lost the Scottish Premiership title to Rangers last term, were expecting a host of personnel challenges was challenging for McKay.
McKay, though, arrived at Celtic Park with a vision to modernise the club, but it emerged last week that he had left his role as the chief executive officer, just 72 days after taking charge.
He is claimed to have stepped down from his role citing personal reasons, but it appears he faced a host of internal challenges during his two-and-a-half months spell at Celtic.
The challenges included differences of opinion on how to move Celtic forward and McKay faced it to the point that he felt his authority was being undermined.
McKay made appointing a sporting director a top priority when he arrived at Celtic, but a disagreement over a prospective change to the model that was in place at the club led to tensions between him and other board members.
It is also said that Gordon Strachan’s return to Celtic as a consultant, while he continued to function as Dundee’s technical director, was another source of tension between McKay and some board members.
While there are suggestions that McKay may have felt Strachan undermined his authority, there are also claims that Celtic were unimpressed with his start as the chief executive officer.
Celtic’s handling of transfers proved to be another source of tension between McKay and other board members, with head of football operations Nick Hammond’s departure leading to major confusion at the club.
Some board members are claimed to believe McKay was too passive in the transfer market, while there are suggestions that the lack of a clear hierarchy on transfers caused Celtic’s struggles in the summer.
Members of the board were also hesitant over McKay’s vision for Celtic, and are now left with the task of appointing a new chief executive officer.
In the absence of McKay, Celtic’s head of legal Michael Nicholson has taken charge as the interim chief executive officer of the club.