Wales winger George North is a doubt for the side's opening Six Nations fixture against Scotland after sustaining a knee injury while playing for his English club Northampton Saints.
North returned from a lengthy lay-off due to a knee ligament injury, which ruled him out of Wales' November internationals, including the defeat to Australia in Cardiff, as a substitute in Saturday's 50-21 defeat by Harlequins and picked up another knock to the same area.
Saints said that the 25-year-old British & Irish Lion star will require up to four weeks of rehabilitation.
"I'm sure George will be diligent in his rehab and we all wish him a swift recovery," Northampton Technical Coaching Consultant Alan Gaffney said on the club's website.
North, who has 69 caps for Wales, is the latest to join a lengthy injury list for Warren Gatland's side, with the likes of Taulupe Faletau, Sam Warburton, Jonathan Davies and Dan Lydiate also sidelined.
Wales kick off their Six Nations campaign against Scotland on February 3.
Six Nations 2018
Saturday February 3
Wales vs Scotland, Millennium Stadium, 2:15pm local, Sunday 1:15am AEDT
France vs Ireland, Stade de France, 4:45pm local, Sunday 2:45am AEDT
Sunday February 4
Italy vs England, Stadio Olimpico, 3pm local, Monday 1am AEDT
Saturday February 10
Ireland vs Italy, Aviva Stadium, 2:15om local, Sunday 1:15am AEDT
England vs Wales, Twickenham, 4:45pm local, Sunday 3:45am AEDT
Sunday February 11
Scotland vs France, Murrayfield Stadium, 3pm local, Monday 2am AEDT
Friday February 23
France vs Italy, Stade de France, 8pm local, Saturday 6am AEDT
Saturday February 24
Ireland vs Wales, Aviva Stadium, 2:15pm local, Sunday 1:15am AEDT
Scotland vs England, Murrayfield Stadium, 4:45pm local, Sunday 3:45am AEDT
Saturday March 10
Ireland vs Scotland, Aviva Stadium, 2:15pm local, Sunday 1:15am AEDT
France vs England, Stade de France, 4:45pm local, Sunday 3:45am AEDT
Sunday March 11
Wales vs Italy, Millennium Stadium, 3pm local, Monday 2am AEDT
Saturday March 17
Italy vs Scotland, Stadio Olimpico, 12:30pm local, 10:30pm AEDT
England vs Ireland, Twickenham, 2:45pm local, Sunday 1:45am AEDT
Wales vs France, Millennium Stadium, 5pm local, Sunday 4am AEDT