The former Manchester City left back limped off during his side's Championship clash with Watford and doubts have emerged over his involvement in Ireland's friendly against Poland
The 21-year-old full back was taken off as a precaution during his side's 2-0 Championship victory over Watford on Tuesday January 29 after sustaining an ankle injury.
"Greg has a knock on his ankle and prudence dictated we take him off a few minutes before the end rather than aggravating it," said Bristol City boss Sean O'Driscoll. "We will know more about his condition after a day or two."
The former Manchester City full back, who joined the Robins in the summer of 2012, has already missed a portion of the season due to a previously sustained ankle ligament injury.
Meanwhile, the Football Association of Ireland (FAI) has confirmed that Everton defender Seamus Coleman will miss the friendly against Poland due to injury.
The former Sligo Rovers right back had been named in Trapattoni's initial 27-man squad on January 21 but has been unable to shake off a thigh injury.