The Manchester United midfielder was the victim of a controversial decision when his stunning free-kick was ruled out for an alleged offence from Jack Hendry in the penalty area.
The defender was adjudged to be offside, while also impeding Unai Simon's ability to stop the set piece as it was whipped in from near the byline.
One man who was less than happy with the decision was McTominay's grandfather who appeared on the midfielder's Instagram story with the caption 'Grandpa not happy with VAR'.
Speaking in the video, he said: "I thought that was bad, I thought that was a winning goal. I was very disappointed with it," to which the Scotland midfielder replied: "So was I".
The decision has made waves north of the border due to the potential impact that it could have on Scotland's qualification for Euro 2024.
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With the result potentially having huge ramifications on the qualification campaign, the SFA have written to UEFA head of refereeing Roberto Rosetti seeking clarification on the confusion and contradictions surrounding the disallowed goal.
This is due to the the referee indicating that it had been disallowed due to a foul on Spain goalkeeper Simon
However UEFA have since confirmed that it was disallowed due to Hendry being offside, leading to significant confusion.
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As a result, SFA chief executive Ian Maxwell has now written to UEFA's head of referees demanding answers over the chronology of events.