Eoin Griffin is out of Connacht’s opening Heineken Cup tie against Saracens in the Sportsgrounds on Friday (8pm), while props Ronan Loughney and Nathan White are rated doubtful.
Centre Griffin is expected to miss about five weeks of action due to a torn foot ligament.
Loughney and White are suffering from concussion and calf injuries respectively.
However, second row forward Michael Swift and out-half Craig Ronaldson are back in contention for the Pool 3 clash.
Coach Pat Lam will announce the starting team on Thursday at midday.
Live radio coverage of Ospreys v Leinster on Saturday Sport from 14:45 on Saturday 12 October on RTÉ Radio 1 and RTÉ.ie (Worldwide).