Rhys Webb faces an extended period out after the foot injury he suffered earlier this month required surgery on damaged ligaments.
The Wales scrum-half saw his World Cup hopes evaporate when he got injured in a final warm-up game against Italy.
And it has now emerged that the injury is more serious than initially feared, with an expected absence of six to eight months, which would effectively rule him out of the Six Nations and beyond.
His club side, the Ospreys, confirmed that he had undergone surgery on his foot, and will now spend at least a month in a protective boot to take the weight off the foot.
"Rhys sustained a significant foot ligament injury that required surgical stabilisation. He has had the surgery and will be non-weight bearing for six weeks and will then wear a protective boot for a further four to six weeks," explained Ospreys medical performance manager Chris Towers.
"Only after that will we be in a position to progress his rehab and, at this stage, Rhys is looking at a six to eight month period out of action, a timescale that reflects the severity of his injury."