Jeff Hendrick has been ruled out of the Republic of Ireland's World Cup qualifier against Serbia tomorrow.
The Burnley midfielder, who missed Saturday's 1-1 draw in Georgia with a thigh problem, worked with the Football Association of Ireland's medical team on Sunday as his injury was assessed, and was then sent for further checks.
O'Neill had hoped to have Hendrick, one of his star men at last summer's Euro 2016 finals, available for a game which could go a long way towards determining Ireland's qualification hopes, but he has not been able to shake off the injury.
The ex-Leicester boss also revealed that Aidan McGeady has gone for a scan on his hamstring and Wes Hoolahan felt some tightness in his groin.
Martin O'Neill: Jeff Hendrick came in and did some work with the medical team. He is still feeling it (the injury). He'll miss out. #COYBIG pic.twitter.com/zPALal6uPi
— FAIreland (@FAIreland) September 4, 2017
The rest of the squad trained at Abbotstown this morning knowing defeat is not an option and perhaps victory will allow them to continue to dream of automatic qualification with the Serbians now two points clear at the top of Group D.
O'Neill said: "We are unbeaten in the group. We are going to try and win the game.
"If we win the game we set ourselves up for a grandstand finish.
"It's a very very important match. We are going into it aiming to win the game."
As the squad trained, skipper Seamus Coleman, who is closing in on a return from the double leg fracture he suffered in March, looked on from the sidelines.
"It's great to see Seamus," said O'Neill. "He's a brilliant captain. He is progressing hugely which is fantastic to hear."
Martin O'Neill: It's great to see Seamus. He's a brilliant captain. He is progressing hugely which is fantastic to hear. #COYBIG pic.twitter.com/uCW2eu3xwx
— FAIreland (@FAIreland) September 4, 2017
Watch the Republic of Ireland v Serbia live on RTÉ2, listen on RTÉ 2fm's Game On and follow the action with RTÉ Sport Online's live blog from 7pm
