Burnley named left-back Erik Pieters in their starting line-up to face Bournemouth in the FA Cup fifth round without realising the defender was suspended.
Pieters picked up yellow cards in each of the previous rounds, earning a one-match ban.
It seems manager Sean Dyche, his coaching staff and Pieters himself were all unaware of the situation, and the 32-year-old was listed on the team sheet for the Clarets.
The club were made aware of the mix-up before kick-off, however, and quickly issued a new line-up with Pieters replaced by the 21-year-old Anthony Glennon.
Had Pieters played in the game Burnley could well have found themselves disqualified from the competition, regardless of Tuesday night's result.
