The midfielder had been training with his national squad in the hope that he could prove his fitness for either or both of Ireland's World Cup qualifiers against Moldova and the Welsh but it appears as though he remains short of being ready.
McCarthy has yet to feature for club or country this season after suffering a knee injury in pre-season. That came in the wake of successive soft-tissue problems last season that severely disrupted his 2016-17 campaign.
The meeting between the two home nations is a big one, with qualification for Russia 2018 on the line. Wales could still win the group depending on how Serbia fare against Georgia while Ireland need to win to keep their hopes alive via the playoffs.
Ireland boss, Martin O'Neill, says that usual skipper Seamus Coleman will very much be in his players' thoughts in what is the reverse fixture to the one in which the Everton fullback suffered a double leg fracture in March.
"Seamus is also a top-class player. We've missed him now for a number of games so we've had our absentees in the past ourselves and we've had to cope and Wales have had to cope without Gareth Bale before.
"I don't know about revenge, but certainly I think the view among the players is that if Russia was available to us and we could make it there, I would think Seamus would be very much at the forefronts of our minds, anyway."