Wales wing Tom Prydie is set to miss the World Cup after learning that he will need knee reconstruction surgery.
The 19-year-old, who became the youngest player ever to be capped by his country last year, suffered the injury while competing in the Magners League for Ospreys against Glasgow.
He is now facing a lay-off of six to eight months, which would mean his hopes of securing a place in the squad for the tournament in New Zealand later this year are over.
"The scans show that Tom has ruptured his anterior cruciate ligament, confirming what we were expecting," Ospreys physiotherapist Chris Towers said.
"Having sought specialist advice regarding the injury, he will now undergo a surgical reconstruction of the ligament later this week once the knee has fully recovered from the initial trauma.
"He is looking at a lengthy lay-off, anticipated to be somewhere in the region of six to eight months."
Prydie made his debut against Italy during the 2010 RBS Six Nations before scoring a try against South Africa and touring New Zealand during the summer.
However, he has fallen behind the likes of Leigh Halfpenny, George North and Morgan Stoddart in the Wales pecking order, meaning he faced a struggle for selection even before the injury.