Sisilia Tuipulotu will miss Wales’ WXV2 opener against Australia on Saturday because of problems with her visa.
The 21-year-old prop should have been training in Cape Town with her team-mates this week.
The Welsh Rugby Union said: “There has been a delay in arranging Tuipulotu’s visa to enter South Africa as a result of unforeseen circumstances.
“All parties are working together to rectify the situation.”
The news comes as a blow to head coach Ioan Cunningham, with Tuipulotu one of his star players.
His options at tighthead now include Donna Rose, Abbey Constable and uncapped Jenni Scoble.
Wales are also facing a potential hooker shortage after Rosie Carr was ruled out of the tournament with a shoulder injury.
Carys Phillips and Molly Reardon are now the only recognised hookers in the squad. It is yet to be seen if another player will be called up.
Cunningham is due to name his side to face the Wallaroos on Thursday.