London Welsh will find out on Tuesday whether their Aviva Premiership fate will stay in their own hands.
The Exiles will appear before a Rugby Football Union competitions hearing charged with fielding an ineligible player - Tyson Keats - in "a number" of games this season.
The scrum-half joined the club from now-defunct Italian club Aironi, and it is understood he was ineligible to play in nine of the 14 games he has appeared in this season.
If Welsh are found guilty they could be docked several Premiership points - potentially enough to relegate them immediately.
Welsh, who had to go through an RFU appeals procedure last summer just to secure their Premiership place, are currently locked in a relegation battle with Sale Sharks and London Irish with five games of the season left.
Sale are currently bottom, but they are just three points behind the Exiles, with Irish a further two points ahead in tenth place.
London Welsh's former rugby manager Mike Scott is also the subject of a separate RFU disciplinary hearing relating to Keats' registration.
He has been charged under RFU Rule 5.12 for "conduct prejudicial to the interests of the Union or the Game". Scott's case will be heard at a later date.
The Exiles will be hoping for some leniency because they themselves brought the matter to the RFU's attention having conducted an internal investigation in February.
In a statement at the time, chief executive Tony Copsey said: "This is obviously a serious matter which the club has not only brought to the attention of the RFU, but is also working closely with the RFU to provide full co-operation while the case is being prepared and ultimately heard.
"Due to the sensitive nature and the impending hearing, the club is unable to make any further comment at this time."