Gareth Owen could miss the entire 2011/12 season after suffering what has been described as a "substantial injury" in training.
The 22-year old Maesteg-born back, who has 50 appearances for the Ospreys under his belt, underwent surgery this week and faces another operation at a later date.
Head physio Chris Towers explained: "Gareth underwent surgery on Thursday after he suffered a knee injury in training.
"It was a bit of a freak accident resulting in him twisting his knee, sustaining a substantial injury.
"As a result of this he will, in all likelihood, be out of action for the whole of the 2011/12 season.
"Thursday's operation was the first part of what will be a two stage surgical procedure to repair the damage and then reconstruct the cruciate ligament.
"At this stage we are unable to say anything more, but will update on his progress as and when we can."
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