Jonny Evans has become the fourth player to withdraw from the Northern Ireland squad because of injury ahead of crunch Euro 2012 qualifiers against Estonia and Italy.
Nigel Worthington's side still retain a slim hope of qualifying should they win their final two Group C games and other results go their way, but will have to do it without Evans, who has an ankle problem.
The Manchester United defender played 90 minutes in his club's 2-0 victory over Norwich last weekend and has started in five of the first six Premier League matches this season.
But with United concerned about the condition of Evans' ankle, he pulled out of the Northern Ireland squad - joining Aaron Hughes (groin) Josh McQuoid (virus) and Jamie Ward (hamstring) as absentees.
"Jonny is not here and he won't be here,'' Worthington told BBC Sport. "He has an ongoing ankle problem. He did play at the weekend but the feeling at his club is that he does need rest and recuperation. We accept that and move on.''
Retiring captain Hughes (groin) was due would to play in what would have been a farewell appearance at Windsor Park in Friday's Euro 2012 qualifier against Estonia, as well as the clash in Italy four days later, but a groin injury has scuppered those plans.
Blackpool's Craig Cathcart is now likely be shifted from right-back to centre-half, while uncapped Preston defender Conor McLaughlin has been added to the original squad to provide another option.
Port Vale's Andrew Little, on loan from Rangers, and Scunthorpe's Manchester United loanee Oliver Norwood were also summoned to offer cover further up the pitch.