Leigh Halfpenny has been ruled out of Wales' clash with South Africa this weekend after failing to recover from concussion.
The full-back sustained the issue in a tackle by Samu Kerevi during a 9-6 victory over Australia on November 10.
After sitting out last Saturday's 74-24 victory over Tonga, Halfpenny showed signs in training this week that he is yet to fully bounce back from the issue, with Hallam Amos now added to the squad as cover.
"Leigh is out," said assistant coach Rob Howley. "He did some training on Saturday morning and was feeling a little bit light-headed. Only common sense.
"George North was back in full training this morning and is available.
"From a back three perspective it gives us an opportunity to look at others.
"Liam Williams has played at full-back, Gareth Anscombe has stepped up there and Hallam Amos has played there."
Including Anscombe at 15 could go some way to solving a growing fly-half selection headache for Warren Gatland, with Dan Biggar having put in a man-of-the-match display when given his chance against Tonga.
"Everyone has debated 10 in Welsh rugby for so many years and that will never change," added Howley.
"It comes down to the skill set and collective cohesion. Gareth Anscombe played particularly well against Australia and Dan was exceptional against Tonga.
"We were very clinical."
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