Burnley manager Sean Dyche revealed he was made aware of Erik Pieters' ineligibility for their FA Cup fifth-round clash against Bournemouth at Turf Moor by a staff member of the visiting team.
Pieters was initially included in Burnley's starting line-up on Tuesday evening despite collecting bookings in the previous two rounds of the competition, earning the Dutch full-back a one-match suspension.
The intervention of Anthony Marshall, Bournemouth's head of media and communications, led to Pieters being replaced before kick-off by Anthony Driscoll-Glennon, with Burnley attributing the switch to an "administrative error".
Dyche refused to blame the late change for Burnley's 2-0 defeat but thanked Bournemouth for their honesty on a night where the Cherries moved into the competition's quarter-finals for only the second time in their history.
Dyche said: "It wasn't disruptive. It was just a simple admin error. We have people who keep an eye on situations, unfortunately it got away from that moment where someone found clarity.
"The rules have changed this year with the booking situation and the number of games in the FA Cup. It was just a clear oversight.
"To be fair to Bournemouth, they flagged it and mentioned it, so credit to them for a bit of gentlemanly conduct. We jumped on it straight away and people at our club held their hands up in the right slots."
Bournemouth caretaker manager Jonathan Woodgate hailed his member of staff for his admission.
He said: "Fair play to the staff who did it and told Burnley. We all want a fair game, so I thought it was important we did that. I think it was Anthony, our press officer, who did it. It's good sportsmanship at the end of the day."
Sam Surridge was instrumental as Bournemouth booked their spot in the sixth round for the first time since the 1956-57 season, opening the scoring midway through the first half on a bitterly cold night in the north west.
Surridge was then upended in the area late on and Junior Stanislas converted the resulting spot-kick to give Woodgate his second win in two games since taking temporary charge following Jason Tindall's sacking last week.
Woodgate said: "I'm loving it, of course. I've been given that responsibility to go and manage a good football club. I'm enjoying it but all I look at is the next game.
"It's just nice to win football matches and increase the confidence in the players.
"We put out a strong team to come here and win the game, there's no doubt about that. It's the second time in Bournemouth's history that they've (reached the FA Cup quarter-finals), so it is good and it breeds confidence."
Pieters' withdrawal meant Burnley made eight changes to the side that drew against Brighton in the Premier League at the weekend, with only Dwight McNeil, Johann Berg Gudmundsson and Matej Vydra retaining their starting places.
They were unable to find the target in the first half but improved after the interval, and Jay Rodriguez spurned a gilt-edged opportunity to level from six yards when he blazed over with the goal at his mercy.
Burnley's defeat to their Sky Bet Championship opponents means they are yet to reach the quarter-final of either of the domestic cup competitions since Dyche took the reins in October 2012.
Dyche, though, said: "With all the changes we've had to make to try to protect the situation and allow us the strength to carry on in the Premier League then it's hard to describe.
"I'm happy of sorts; there were some good performances and a lot of commitment and effort to get a win. Inevitably you're disappointed because we conceded two really poor goals.
"But the team had a go, they gave everything, it's just they couldn't find the key moments."