Williams joins an extended injury list at the Ospreys

The Ospreys captain, 32, is due to see a consultant on Monday and will know more after his medical assessment.

"This is another serious blow for the Ospreys and means another senior player out for an extended period," said Ospreys manager Derwyn Jones.

"Barry is a true professional and I am sure he will recover from this injury in the minimum time possible."

Promising 22-year-old Swansea RFC hooker Richard Hibbard has been handed the Ospreys number two jersey for his side's daunting trip to Stade Francais.

It gives an opportunity for Huw and Richard to show us what they are capable of Derwyn Jones

Huw Bennett, who was dropped from the Wales international squad this week, is relegated to the bench.

"Although Barry's injury is a setback it gives an opportunity for Huw and Richard to show us what they are capable of," said Jones.

The Celtic League champions have had a torrid season with injuries.

Brent Cockbain (hamstring), Ryan Jones (shoulder reconstruction) and David Bishop (fractured kneecap) are all out for the season, and Paul James' neck injury is currently being assessed.

A host of other injuries and suspensions have contributed to exits at the group stages of the Heineken Cup and Powergen Cup.

They are one-from-bottom in the Celtic League, the lowest of the Welsh regions, and face a season-long battle to win Heineken Cup qualification for next season.