The Highlanders will have to undertake further tests on wing Patrick Osborne, lock Joe Wheeler and flanker Dan Pryor to confirm whether they can play against the Waratahs this Friday.
The three were all injured in the Highlanders match against the Lions last weekend.
All Blacks wing, Waisake Naholo and Fumiaki Tanaka are already out due to injury.
The Highlanders defeated the Waratahs 40-35 when they met in a warm-up match last month.
The Waratahs play the Highlanders at 8.40pm Friday while Western Force will take on the Hurricanes at 6.35pm.
Source: Stuff.co.nz
