Tommy Bowe has given Ireland a major injury scare ahead of this season's RBS 6 Nations Championship.
The British and Irish Lions Test wing and prolific try-scorer will miss the Ospreys' Heineken Cup clash against Toulon tomorrow.
Coach Declan Kidney must now await news over Bowe's availability for the opening Six Nations appointment with Italy in Rome on February 5.
Ospreys physiotherapist Chris Towers said: "We've withdrawn Tommy from this weekend's game on medical grounds, pending further investigation and specialist opinion for a knee problem.
"Due to the onset of some recent symptoms, we scanned him this week, which highlighted an issue that could potentially develop into something problematic.
"As such, we felt that it is in Tommy's best interest to take these precautions.
"We have notified the Irish medical team, and following further investigations next week we should be able to establish the most appropriate course of treatment for the problem and to confirm whether it will interfere with Tommy's involvement in the Six Nations with Ireland."
Bowe, 26, is rated among the most dangerous wings in European rugby and is a major part of Kidney's Six Nations plans. He has scored 16 tries in 36 appearances for Ireland.
There is good news in the Ospreys' selection, though, for Wales coach Warren Gatland, with star wing Shane Williams set to launch his comeback tomorrow.
Williams, a former world player of the year, dislocated his shoulder during Wales' defeat against South Africa in November.
But he has been named on the Ospreys bench, handing Gatland a considerable boost after losing three key players - Adam Jones, Gethin Jenkins and Tom Shanklin - through injury for the entire Six Nations tournament.