Ulster were dealt a heavy blow on Tuesday when Charles Piutau, Sean Reidy and Rob Lyttle were all ruled out for some considerable time with injury.
Piutau and Reidy retired injured during the first half of Ulster's 59-10 win against Southern Kings in the Guinness PRO14 last Friday night at Kingspan Stadium.
Piutau dislocated a rib cartilage and he will be unavailable for selection for a number of weeks.
Reidy sustained a medial ligament knee injury that will keep him out of action for approximately six weeks
Lyttle was forced off after he scored the second of two tries - and it was confirmed on Tuesday he had suffered a hamstring injury of significance and he is expected to return to playing in 4-6 weeks.
Ulster Rugby also confirmed Andrew Trimble (back) and Peter Nelson (hamstring) have returned to training and are in contention for Friday's clash versus Edinburgh in Belfast