Darron Gibson is the Republic of Ireland's latest fitness doubt for the Euro 2012 play-off against Estonia.
The Manchester United midfielder is out of action as his recovery from a foot injury is taking longer than expected.
Sunderland defender John O'Shea is said by his boss Steve Bruce to be out for "two to three weeks" with a hamstring injury, so he is set to miss out.
Leeds defender Darren O'Dea could also miss out after suffering concussion in Sunday's 1-1 draw against Cardiff City.
Gibson resumed light jogging last week but he remains out of action with the first leg in Tallinn on 11 November looming.
O'Shea sustained his injury in Saturday's draw with Aston Villa.
However, skipper Robbie Keane has provided a boost for the Republic after returning to action for LA Galaxy on Sunday.
Keane, who missed the last qualifying win over Armenia with a muscle injury, played for 83 minutes on his return for Galaxy in the 1-0 win over New York Red Bulls.
He is now poised to lead the attack in the first leg in Estonia on 11 November and the return leg in Dublin four days later.
His availability is vital with Wolves striker Kevin Doyle suspended for the first leg and West Brom's Shane Long a major injury doubt.
O'Dea suffered a bang on the head in Leeds's previous game against Birmingham, then sustained another knock in the Cardiff draw.
"He had a lack of vision down one side and a bit of blurriness as well, so he's got concussion," said Leeds manager Simon Grayson.
Gibson has been unable to hold down a regular starting place for the Republic with manager Giovanni Trapattoni usually favouring Keith Andrews and Glenn Whelan in central midfield.
Republic of Ireland: Given (Aston Villa), Westwood (Sunderland), Forde; O'Shea (Sunderland), Kelly (Fulham), Ward (Wolves), Dunne (Villa), St Ledger (Leicester), O'Dea (Leeds), McShane (Hull); Whelan (Stoke), McCarthy (Wigan), Coleman (Everton), Andrews (Ipswich), Fahey (Birmingham), Gibson (Man Utd), Keogh (Leeds), Duff (Fulham), McGeady (Spartak Moscow), Hunt (Wolves), Lawrence (Portsmouth); Keane (LA Galaxy), Doyle (Wolves), Long (West Brom), Cox (West Brom), Walters (Stoke).