James McCarthy could miss Ireland's vital World Cup qualifying game against Austria next month.
It is being reported that the Everton midfielder suffered a hamstring injury in training and is set for a three-week layoff.
McCarthy's Everton manager and Republic of Ireland manager Martin O'Neill have previously been at loggerheads over McCarthy's fitness.
The Scottish born player started this month's games against Georgia and Moldova despite missing training at the Merseyside club, as he was recovering from a hernia operation.
Shane Long is also a doubt for the game having sustained a knock while playing for Southampton against Internazionale in the Europa League.
Ireland currently sit second in the group behind Serbia on goal difference.