Wales wing George North looks set to miss the autumn internationals after suffering a sprain to his posterior cruciate ligament.
The injury will require six to eight weeks' rehabilitation, North's club side Northampton have confirmed, a timescale that could see the 25-year-old miss Wales' games against Australia, Georgia, New Zealand and South Africa.
North was initially hurt during a tackle by Saracens centre Brad Barritt as Northampton were beaten 57-13 at Franklin's Gardens in the Champions Cup on Sunday.
He attempted to run the injury off after receiving medical treatment but he collapsed shortly after and was replaced by Tom Collins on 29 minutes.
North had been instrumental in helping Saints' make a strong start to the season, although they were outclassed by European champions Sarries.
The 25-year-old, who has represented Wales 69 times, has seen his recent career blighted by a succession of concussions but after a disappointing British and Irish Lions tour of New Zealand, he had returned to form.