Michael Evans is out of the Republic of Ireland's World Cup play-off against Belgium at Lansdowne Road on Wednesday. He sustained a double fracture of the cheekbone in training yesterday.
It happened when he collided with Jason McAteer and he left soon afterwards for an X-ray which revealed that the damage was more severe than had been anticipated. He will also miss the second leg of the tie in Brussels on November 15th.
"It's a setback for the squad and a big disappointment for the lad himself," said McCarthy. "These things are unfortunate but they are always liable to happen when players are moving at full pace in training."
Neal Fenn, a member of the under-21 squad , has been called in to fill the vacancy caused by the withdrawal of Evans. Fenn was in Dublin for last night's awards ceremony and duly accepted an invitation from McCarthy to join the squad.
Together with Motherwell's Tommy Coyne, he will provide the cover for the first choice strikers Tony Cascarino and David Connolly.
Ironically, Evans, who transferred from Southampton to West Bromich last week for a fee of £750,000, was recruited by McCarthy only last month because of the dwindling number of options available to him in the front line.
In quick succession, the manager lost Keith O'Neill, Niall Quinn, Jon Goodman and Alan Moore. He thus had to accelerate Evans's international debut, and recall Tommy Coyne after an absence of almost 18 months.
Quinn has been given the all clear to resume full training this week after his latest knee injury but it remains to be proven if he can deliver on his pledge to present himself fully fit for selection for the return meeting with the Belgians in just under three weeks.
Evans made a brief five-minute appearance as a replacement for Tony Cascarino in the 1-1 draw with Romania at Lansdowne Road earlier this month, and in the sense that he was never going to start the game on Wednesday, yesterday's collision may not be unduly expensive. Yet, it tended to depress spirits on a day when McCarthy was embarked on the challenge of focusing minds for the big game.
Nor was that the only injury scare in the camp. Terry Phelan, the Everton full back, was kicked on the ankle in training on Saturday and and was left out of yesterday's session as a precaution. He is expected to participate, however, when the players train behind closed gates at Kilkea Castle outside Athy, Co Kildare, this morning.
As a concession to Ray Houghton's 35 years and the fact that he has played three times in eight days, he too was excused training yesterday. Like Gary Breen, who is recovering from a cold, he is likely to be involved when some setpieces are rehearsed today.
The growing hope surrounding the game, reflected in an even bigger media presence than usual and the number of fans presenting themselves at the squad's headquarters at Dublin Airport, is responsible for the move to Co Kildare.
But McCarthy was at pains to emphasise that the increased attention is not wholly unwelcome. "It can be irritating when people ask you for match tickets which you haven't got but it's still encouraging to find that public interest is running at such a high level," he said.
As ever, he is miserly in proffering information about his team plans but he surprised nobody with the information that he does not intend to play two wingers. "We cannot afford to surrender midfield by playing an extra winger, it would be folly to try it," he said.
He confirmed that he had consulted with Bobby Gould, the Welsh team manager, who twice encountered the Belgians in the qualifying series, losing by a goal in each instance. Gould is convinced that Ireland can win the tie - providing they don't give the opposition too much respect and avoid playing too much through the middle.
Gould's advice to the Irish manager was to hit the front men with the early ball from the back and vary the match plan by getting in deep crosses. It's not a million miles from the strategy which Jack Charlton implemented so successfully in another era. Did it not run counter to McCarty's philosophy on the game?
"I never at any stage precluded the long ball from our match plan, just as I never insisted that the correct approach was to channel everything through the middle. As a defender myself, in my playing days, I was never particularly worried about people coming at me.
"It is the ball played in behind the back four, the one which makes them turn, which gets defenders into trouble. And this, of course, will be reflected in the way we go about winning the game on Wednesday."
Tony Cascarino, who has scored five times since the home game against Liechtenstein in May, was described by McCarthy on Saturday as the biggest surprise of his qualifying programme.
"I expressed reservations after the game in Macedonia in April about Cas's future in the squad, and had there been an alternative available, who knows what might have happened," he said. "Now I'm happy to admit publicly that I was wrong. And I'm delighted for Tony whose attitude throughout has been superb."
Belgium arrive in Dublin this afternoon amid reports of growing tension between manager George Leekens and some of his senior players. It follows Philippe Albert's retirement from international football in midweek, a decision which was seen as the player's response to his shock sacking from the team which beat Wales earlier this month.
Leekens was quoted at the weekend as saying that team morale had not been damaged by Albert's precipitative action but it remains to be seen how he goes about disguising the loss of one of his experienced international campaigners.