An unnamed Republic of Ireland player will miss Wednesday night's UEFA Nations League game in Finland after a third Covid-19 test confirmed that he had contracted the coronavirus.
The late-night statement from the FAI followed a dramatic day when the player first tested positive and then negative in a second test.
The player will now have to isolate for ten days, and no replacements will be called up to the squad.
The FAI said that no members of the squad or the backroom team have been identified as close contacts of the player.
Stephen Kenny's preparations for the game had been thrown into further disarray when the player received a positive result for the virus from the UEFA testers on Sunday.
However, the FAI medical team organised a second test for the player, which returned a negative result on Monday afternoon.
The player was then tested for a third time as the team was due to fly to Finland on Tuesday morning and was subsequently found to have the virus.
Five players were ruled out of Sunday's 0-0 draw with Wales due to the first positive case in the squad and with those players still missing, Kenny had already bolstered his options by calling up six additional players for the trip to Helsinki.
The sextet includes Adam Idah and Aaron Connolly, who missed the Euro 2020 play-off defeat to Slovakia and match against Wales, as they were deemed close contacts of an FAI staff member who tested positive for Covid-19 in Bratislava.
It subsequently emerged that the staff member's test was a false positive, meaning Kenny was needlessly denied two attacking players for the play-off, a match that was decided by a penalty shootout.
The entire Ireland squad was tested once more on Sunday night, when the second positive case was first detected.
"We do need to review with UEFA and the HSE on the protocols itself and if they are fit for purpose for international games," he said.
"This is all new for everybody. Everybody will pick up exactly what are the key learning points. I think in particular UEFA and the HSE because we follow their protocols, we have to feed into them exactly what we think could be changed as a result of it.
"You need testing on the ground, you can't just have testing coming in. We need very quick results to the testing because if you need to add squad players you have to do it quickly."