Wing Owen Lane has been released from Wales' Six Nations squad following a "significant hamstring injury" sustained in training.
The Cardiff Blues player, 21, has won two caps and scored a try on his debut against Ireland in August 2019.
Wales have not yet called up a replacement for Lane.
A Welsh Rugby Union statement read: "Further assessments will be concluded early next week to establish an accurate prognosis."
Wales begin the defence of their Six Nations title at home to Italy on Saturday, 1 February.
Head coach Wayne Pivac has an abundance of options on the wing, with 2019 World Cup top try scorer Josh Adams, George North, Leigh Halfpenny and uncapped duo Louis Rees-Zammit and Johnny McNicholl among those who could play there.
North, Adams and Lane have also been tipped to plug the midfield gap created by Jonathan Davies being out injured.
Pivac has said North is an "exciting" option for that role.
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