Ospreys have lost Jeff Hassler and Tyler Ardron to injury ahead of their European Challenge Cup debut.
Ospreys start their campaign at home against the Newcastle Falcons on Friday, but they will have to do so without Hassler and Ardron.
Hassler has been ruled out for nine months with an Achilles injury he sustained during the 46-24 thrashing of Cardiff Blues last Friday night.
Fellow Canadian Ardron will be out for two months and is doubtful for the first four rounds after dislocating his thumb in the 9-7 defeat to Ulster the previous week.
"Tyler suffered a dislocated thumb which required a small surgical procedure at the end of last week. His recovery will keep him out for up to eight weeks," Ospreys Medical Performance Manager Chris Towers confirmed.
"Jeff sustained an Achilles tendon injury on Friday night and investigations over the weekend, and discussions with specialists, have confirmed the injury doesn't require surgery. However, he will be out of action for a prolonged period, with an initial prognosis of six to nine months."