Birmingham City midfielder Ruesha Littlejohn was shown a yellow card in Sunday's 1-1 draw with Reading
Birmingham City have been charged by the Football Association with playing midfielder Ruesha Littlejohn when she should have been suspended.
The 30-year-old, who has also been charged, played all of Sunday's 1-1 Women's Super League draw with Reading.
Blues are understood to have been under the impression that she had served her ban in the previous weekend's Women's FA Cup win over Coventry United and put it down to "an administrative error".
They have until Tuesday to respond.
The case is now expected to go to an FA tribunal and could have repercussions on the WSL relegation battle.
After their successive 1-1 draws against Reading and local rivals Aston Villa on Wednesday, Blues have edged three points clear of the one relegation spot, currently occupied by Bristol City.
But, if a points deduction were to occur, that might put Blues' WSL place in jeopardy.
The breach of FA Rule E12 is that "Birmingham City Women failed to ensure that a player registered with the club complied with an automatic suspension".
Blues say they "unequivocally support Littlejohn" but will make no further comment.
Birmingham have two games left to play, at title contenders Manchester City on Sunday before ending their campaign at home to Tottenham on 9 May.
