Burnley named left-back Erik Pieters in their starting XI to face Bournemouth in the FA Cup fifth round before realising the defender had been suspended.
Pieters was given a one-match ban after picking up a yellow card in each of the previous rounds.
Burnley were made aware of their mistake by a member of the BT Sport team and subsequently replaced Pieters with the 21-year-old Anthony Driscoll-Glennon.
Burnley's official Twitter account announced the change by saying: 'Due to an administrative error, Erik Pieters no longer plays tonight and Anthony Glennon will come in for the left-back.'
While commentator Paul Dempsey said: ‘It was a very late change to the Burnley team selection tonight.
‘We’re all very indebted to out stats man, Joel Miller, who correctly pointed out that he believed Erik Pieters, named in the original team, was in fact suspended for this game.
‘The consequences of that for Burnley could have been very severe. ‘Driscoll-Glennon went onto the team sheet after our reporter, Natalie Quirk, made the enquiry of Burnley.’
Burnley could have been disqualified from the competition - regardless of the result - if they failed to remove Pieters from the squad.
Such an event would have crushed the club's aim to reach the quarter-finals for the first time since 2002-2003.
Driscoll-Glennon is yet to represent Burnley in the Premier League this season. His only senior appearances have been during his loan spell at Grimsby Town last season.
The youngster was, however, used as a substitute in both the FA Cup and EFL Cup previously.