The 30-year-old suffered a minor tear to cartilage in his right knee during the Ospreys' defeat to Munster 11 days ago.
It now looks almost certain that the Clermont Auvergne-bound fullback has played his last game for the Swansea-based region and he is unlikely to feature against the Baa-Baas in five week's time.
"We are currently seeking specialist advise for a right knee problem and a decision will be made in the next couple of days regarding management and prognosis," said Ospreys physio Chris Towers.
"It looks unlikely that he will be available to take any further part for the Ospreys this season, even if we make the play-offs, but we remain positive that this will not impact on his availability for the Rugby World Cup."
The Ospreys need a bonus-point win against Aironi on Friday and other results to go their way if they are to sneak into the Magners League play-offs on the final weekend.
But they will also be without fellow Lion Shane Williams who has failed to recover in time from the knee injury he suffered in the Six Nations showdown with Ireland.
"We've tried but Shane just hasn't made it for this week," added Ospreys head coach Sean Holley.
"If we are fortunate to make the play-offs then he maybe available for that. But this game has come too early for him and us and we'll have to reassess of we qualify but I don't think there are any issues for later in the summer."