The Waratahs have lost fullback Bernard Foley and flanker Chris Alcock for Sunday's Super Rugby match against the Crusaders in Sydney.
Scans have revealed that Foley has aggravated a previous shoulder injury and is expected to miss up to three weeks of rugby.
Foley's loss has been made worse by a foot injury to forward Paddy Ryan and appendicitis surgery for flanker Alcock.
Ryan has sustained a Lisfranc (mid-foot ligament) injury to his right foot and is expected to miss around six weeks.
Alcock surgery on Sunday for appendicitis but in addition to the injuries the Waratahs have lost centre Rob Horne for two weeks to suspension for his dangerous tackle on Kurtley Beale.
The Waratahs already have an injury list containing Dan Vickerman (shoulder/leg), Drew Mitchell (ankle), Lachie Turner (hamstring), Damien Fitzpatrick (knee) and Pat McCutcheon (ankle).
Waratahs coach Michael Foley has said that he will consider playing No.10 Berrick Barnes at fullback but the most likely is Adam Ashley-Cooper.