Jonathan Davies has been ruled out of this year's Rugby World Cup with a ruptured anterior cruciate ligament.
The 27-year-old Wales international suffered the injury during his Clermont Auvergne side's recent encounter against Montpellier.
Having been advised to undergo surgery immediately, the centre will now be sidelined for up to seven months.
"It's a disappointment for Jonathan and for us, but the advice is for him to have the surgery straight away," Wales head coach Warren Gatland said in a statement.
"Obviously the injury rules him out of the 2015 Rugby World Cup but our focus is his long term career and we will be working closely with him during his recovery looking towards the 2016 RBS 6 Nations."
The tournament gets underway on Friday, September 18, with Wales playing their first encounter against Uruguay at the Millennium Stadium two days later.
Liam Apicella
