Our full-back raider picked up an ankle injury earlier in the week and reported that the problem was sore after training on Friday.
Boss Mick McCarthy has delayed naming his side to give the 24-year-old the best possible chance of being fit to play.
It would be a huge blow for Stephen to miss out. A hernia problem ruled him out of many key games for us last season and his return came as we lost the FA Cup semi-final against Arsenal.
He started to hit his top form at the end of the season and, having recently expressed his desire to win his international place back from Gary Kelly, he would be devastated to miss out.
Stephen Carr has emerged as the big injury doubt for the Republic of Ireland's crucial World Cup qualifier against Portugal on Saturday.