James McCarthy is out of the Republic of Ireland's opening World Cup qualifier in Serbia after returning to his club following assessment of his groin injury.
The 25-year-old midfielder met up with Martin O'Neill's squad despite missing Everton's 1-0 Premier League win over Stoke at the weekend with the problem, but has had to admit defeat in his efforts to shake it off ahead of Monday night's game in Belgrade.
A Football Association of Ireland statement said: "Midfielder James McCarthy returned to his club following assessment from the FAI medical staff as he recovers from a groin injury."
The news was confirmed amid speculation that McCarthy's injury will require surgery to repair, and that his fitness scuppered any chance of a deadline day move away from Goodison Park, with new manager Ronald Koeman apparently prepared to let him leave.
However, the former Hamilton and Wigan was included in the Toffees' 25-man squad which was submitted to the Premier League following the closure of the summer transfer window.
O'Neill now faces the task of finding a replacement for a man who came of age at the Euro 2016 finals in France, with Harry Arter, Stephen Quinn and David Meyler among those contesting the vacancy.
Former skipper Robbie Keane has left the camp after formally retiring from international football after scoring in Wednesday night's 4-0 friendly victory over Oman, while Dundalk keeper Gary Rogers will travel to Serbia on Saturday as back-up to Darren Randolph and Keiren Westwood after David Forde opted to stay with new club Portsmouth.