Burgess Hill are facing Senior Cup elimination for fielding the cup-tied Dave Stevens.
Their hopes of an FA Vase lifeline have also been dashed after third round victors Arlesey were found not guilty of making four substitutions.
Stevens scored and was sent-off as high-flying Hillians won 2-1 at Selsey last Saturday.
He had also played in the competition for Lewes against Bosham on October 7.
The Sussex FA were last night still awaiting Hillians' match return card.
But county secretary Ken Benham said: "We have received the referee's card which confirms Dave Stevens was sent-off and we also know he played for Lewes.
"Burgess Hill will be expelled from the competition pending confirmation from the club themselves."
Stevens also played when cup-tied as Hillians crashed 4-1at Arlesey in the Vase.
Boss Gary Croydon believed the hosts made too many substitutions during that match but an FA spokesman said: "We have received the referee's report and asked the club to account for their substitutions and it is apparent only three were used."
Hillians are holding an internal enquiry into both cases.
Boss Gary Croydon said: "We have not been charged with anything and we did not play an ineligible player knowingly.
"We believe we have acted on incorrect information and I will leave other people to decide where that information came from."
Benham has reminded clubs they can call the Sussex FA to check the availability of their players for cup competitions.
Full-strength Hillians face Horsham YMCA at Leylands Park tomorrow in the Rich City League's match of the day.
Croydon added: "If people want to talk about our football I can tell them we are firing at the moment. We are really playing well."
Horsham YMCA expect to recall Warren Tilley, Phil Fitzgerald and Matt Duffield but Glen Newall (neck) and Barrie Westgate (back) are ruled out.
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