Chesterfield face expulsion from the FA Cup after being charged with fielding an ineligible player.
On-loan Wolves defender Georg Margreitter featured in the 1-0 win at MK Dons without written permission from his parent club.
The Spireites were handed a potential trip to Scunthorpe or Worcester City in Monday's third-round draw.
But their place is in jeopardy, and the League One club have until 17:00 GMT on Thursday to respond to the charge.
A Football Association statement said: "The FA has charged Chesterfield with a breach of FA Cup rules, after allegedly fielding an ineligible player."
Chesterfield executive Chris Turner said: ''We had a verbal agreement to play Georg but unfortunately we did not ensure that the consent was received in writing.
"We will of course provide the FA with our full co-operation as they investigate the matter."
But Bradford City were reinstated on appeal two seasons ago, after initially being expelled from the competition for playing on-loan Newcastle United defender Curtis Good in their 1-1 second-round draw with Brentford.
Worcester City and Scunthorpe will contest a second-round replay at Aggborough on Wednesday, 17 December.