The SRU chief is set to visit a potential site for a new stadium in Stirling this week not far from the battlefield where Robert Bruce relieved Stirling Castle from the hands of the English monarch, Edward II.
But Mackay maintains the trip is not set to free the imaginations of the most nationalistic Scot.
He told The Herald: "Someone is being very mischievous here.
"We were told in November about a plot of land being available, and I feel, as chairman of the SRU, I am duty bound to investigate every possibility.
"However, I think it is an indication of the priority that we are giving to this that I am only visiting it this week."