Martin O'Neill has called on UEFA to act over the Danish dispute which threatens to turn the Republic of Ireland's Nations League group into a farce.
Denmark's preparations for their opening game in the competition against Wales are in turmoil following a row between the Danish Football Association and their players' association.
It could lead to Denmark fielding a scratch side of third-tier and indoor futsal players in Aarhus on Sunday, rather than established performers like Christian Eriksen and Kasper Schmeichel, and leave the Republic at a serious disadvantage in the group.
"If it does develop this way there would certainly be a degree of unfairness about it," said O'Neill, who will take charge of his 50th game as Irish manager tomorrow.
"I think everyone would accept that if Denmark play players from lower divisions against Wales then it certainly gives them a massive advantage.
"I think UEFA probably should (act), and will as well, if it develops in the direction that it looks as if it is going. UEFA will have to make some sort of statement about it then.
"It wouldn't be fantastic news for the competition itself, but we have to see if things get resolved in the next couple of days and Denmark play their full-strength side."
"The competition has a bearing on the European Championships later on," he said.
"Despite the fact that there seems to be a feeling that no-one totally understands what it's about, I think we've got the gist of it.
"If you pare it down this competition has taken the place of a play-off situation for some third-placed teams, so I think it is really important."
Meanwhile, O'Neill, has confirmed that Stoke City's James McLean broke his wrist in two places during an accident in training yesterday.
O'Neill said the Stoke winger had still wanted to play before accepting he needed surgery on the injury.
Alan Browne of Preston has also been ruled out of the game against Wales with a calf injury.
Browne joins James McClean, Robbie Brady, James McCarthy, Scott Hogan and Shane Long on the casualty list.
The plus for O’Neill is that he has the nucleus of his first-choice defence with the likes of Seamus Coleman, Shane Duffy, Ciaran Clarke, Kevin Long and Stephen Ward all available and it's likely that they will be a busy five against a formidable Welsh side boasting Gareth Bale, Aaron Ramsey and Joe Allen.
The Republic of Ireland squad trained at the Cardiff City Stadium this evening ahead of a meeting with a Wales team managed by Ryan Giggs in his first competitive fixture in charge.
Giggs said earlier today that he didn’t consider tomorrow night's game as a revenge tie after the World Cup qualifier defeat against the Republic last year.
Follow Wales v Republic of Ireland with our live blog on RTE.ie and the RTÉ News Now App and listen to live commentary on 2fm's Game On from 7pm