Waterford have made a complaint to the FAI over the eligibility of Finn Harps defender Shane McEleney, who played in their 1-0 loss to Harps on Monday night.
Harps won the crucial League of Ireland Premier Division clash thanks to a first-half goal from Adam Foley.
The result secured top flight safety for Harps and sent Shelbourne to a promotion/relegation play-off against Longford Town.
For Waterford, it meant they missed out on a top four finish. Fourth place could be enough for a European spot if one of the top three - Shamrock Rovers, Bohemians and Dundalk - go on to to win the FAI Cup.
McEleney received his fifth yellow card of the season in Harps' clash with St Patrick's Athletic on Wednesday, October 28th.
In normal circumstances, he would have served a one-match ban on the week beginning Monday, November 9th.
However, the FAI decided to move the 'effective date' for suspensions to Tuesday, November 10th because the final round of league fixtures was delayed after Shamrock Rovers' clash with Derry City had to be pushed back due to Covid-19.
In a statement issued today, Waterford said: "Waterford FC can confirm that a complaint has been registered with the FAI regarding our Monday night fixture away to Finn Harps. The matter is with our legal team and no further statement will be made on the matter at this time."