James McCarthy's groin injury is being monitored as Republic of Ireland boss Martin O'Neill begins preparations for next Monday's tough opening World Cup qualifier in Serbia.
The Everton midfielder reported for international duty nursing the problem which kept him out of Everton's Premier League victory over Stoke at the weekend, and his chances of being involved in Wednesday's friendly against Oman in Dublin look extremely remote.
His condition will continue to be assessed along with a series of other fitness concerns.
Central defender John O'Shea is due to meet up on Tuesday after staying at club Sunderland for recuperation following the hip injury he suffered in the 2-1 derby defeat by Middlesbrough on August 21.
Strikers Robbie Keane - the 36-year-old will make his 146th and final appearance for his country against Oman before retiring from international football - and Shane Long both sat out training at Abbotstown on Monday after with minor knocks, but neither are real doubts.
There was better news too of Everton full-back Seamus Coleman, who is yet to play for his club this season because of an ankle problem, and Derby midfielder Jeff Hendrick, who is nursing a hamstring strain.
Both did some light training and Coleman in particular is optimistic that he could be ready for the Serbia game.