Wales hooker Richard Hibbard will miss the Ospreys' Christmas fixtures after chipping a bone in his hand.
He suffered the injury in the Heineken Cup win over Castres and is out of the Cardiff Blues and Scarlets games.
The region are hopeful the British and Irish Lion will be fit for the return Scarlets game on 3 January.
"[The injury] is likely to rule him out [of] the away games against Cardiff and Scarlets," said Ospreys physio Chris Towers.
"We expect this to settle fairly quickly though and remain optimistic about his prospects of being available for the game against the Scarlets at the Liberty Stadium."
The Hibbard injury comes just days after it was announced he was to leave the Ospreys for Gloucester at the end of the season.
He said he was "gutted" to be leaving and complained there was not enough funding in Welsh rugby to keep top players playing in Wales.
"I'm absolutely gutted to be leaving my home region, where I've been all my career," he told the Ospreys website.
"It's unfortunate that there isn't the funding to allow boys who want to play in Wales to stay in Wales."
Injury-hit Ospreys centre Andrew Bishop has also been ruled out of action for at least four months after having back surgery.
"Andrew has undergone surgery in an attempt to correct the same longstanding back problem that ruled him out of action last season," said Towers.
"It is difficult to predict timescales for a return to action for him, but we are looking at a best-case scenario of around four months."