Jamie Nutbrown will be out of action for around two months after breaking his left foot in the match against Glasgow Warriors.
The 27-year-old scrum-half only arrived at the club last week and his injury leaves Ospreys short of nines, with only Rhodri Wells and teenager Rhys Webb currently available.
Chris Towers, the Ospreys physio commented, “He has been reviewed by a specialist, who unfortunately confirmed that Jamie will need to spend the next four weeks in plaster. That will be followed by a period of strengthening and rehabilitation. All in all we could be looking at an eight-week lay-off.”