Ulster have been left with a considerable casualty count following their Heineken Cup quarter-final defeat to Saracens on Saturday.
Scrum-half Ruan Pienaar, hooker Rory Best, lock Dan Tuohy and No 8 Roger Wilson will all be sidelined for lengthy periods after being injured during the 17-15 defeat at Ravenhill.
Pienaar suffered a recurrence of shoulder trouble and now faces at least six weeks on the sidelines, while Ireland international Best sustained what Ulster described as "a significant ankle sprain" and will be out for between six and eight weeks.
Ulster also confirmed that Tuohy will undergo surgery this week to repair a fractured hand, with Wilson absent due to a fractured thumb.
Wing Andrew Trimble, meanwhile, will follow return-to-play protocols after being concussed in the Saracens clash, and prop John Afoa's back injury means he will miss the RaboDirect PRO12 appointment with Connacht on Friday.
Meanwhile, full-back Jared Payne will face a disciplinary hearing on Wednesday following his red card in the defeat.
Payne was dismissed after just five minutes at Ravenhill by French referee Jerome Garces for an alleged dangerous charge on his opposite number Alex Goode, who was stretchered off the pitch.
Ulster are currently third in the PRO12, well on course to make the play-offs as they prepare for remaining regular-season games against Connacht, Glasgow, Leinster and Munster.