Slovakia midfielder Stanislav Lobotka has been ruled out of Thursday's Euro 2o20 playoff semi-final with the Republic of Ireland.
The 25-year old has not been released by his club Napoli.
Lobotka had been identified as one of Slovakia's key players by Ireland manager Stephen Kenny.
Slovakia were already without first-choice goalkeeper Martin Dubravka due to an ankle injury.
The Napoli squad had been in an isolation bubble after two members of the squad - Piotr Zielinski and Eljif Elma tested positive for COVID-19.
Napoli were forbidden from travelling to Turin for last weekend's Serie A game with Juventus.
The latest round of swabs at Napoli all returned negative, except that of Lobotka which is still being processed.
"We did our best," Slovakia coach Pavel Hapal said of their attempts to emancipate Lobotka, "The problem was in communication, Napoli stopped communicating."
"It's astonishing. For example, players from Juventus could go to the national team matches. We will miss him."
Slovakia's preparations have been further complicated by their latest batch of COVID-19 tests.
All returned negative, bar that of one player whose result was inconclusive.
Each of the last four meetings of Ireland and Slovakia have ended in draws, something which cannot happen in Thursday's one-legged affair.
"It's time to break it," said Slovak talisman Marek Hamsik of their recent record, "This is the right match. But it won't be easy.
"It's an extremely important match. We watched the opponent's videos and we know what they are strong and what we should avoid.
"We have to concentrate. just for ourselves and especially to improve on previous matches. We have already been able to beat Scotland, for example."