Tottenham defender Ben Davies will have an operation on a broken ankle that could rule him out of Wales' World Cup play-off.
The 32-year-old was given oxygen before being carried off on a stretcher after 19 minutes of Saturday's 2-1 Premier League defeat by West Ham.
"We can confirm that Ben Davies will undergo surgery today for a fracture of his left ankle," read a Spurs statement.
Tottenham did not give a timeframe on how long Wales captain Davies would be out for.
Wales face Bosnia-Herzegovina in the World Cup play-off semi-final at Cardiff City Stadium on 26 March, with the winners at home to Northern Ireland or Italy in the final on 31 March.
Davies joins a growing injury list for Tottenham, while manager Thomas Frank is under scrutiny with only seven wins from 22 league games this season and Spurs 14th in the table.
Spurs fans chanted "you're getting sacked in the morning" to Frank, who was appointed in June, during the closing stages against West Ham.
Tottenham have held talks about Frank's future but he remains in charge before the Champions League game against Borussia Dortmund on Tuesday.
Wales manager Craig Bellamy recently described Davies as his "best player", which tells you all you need to know about how much he will be missed should he not be available for the World Cup play-offs.
He is the only player in the squad to reach 100 caps and is a veteran of the Euro 2016, Euro 2020 and the 2022 World Cup campaigns.
That experience on and off the pitch for such a crucial game against Bosnia-Herzegovina in March is priceless.
Wales have coped without their captain, who missed much of their qualification campaign with a hamstring problem, to finish second in their group behind Belgium.
The now-regular Premier League experience of Leeds's Joe Rodon and rapid development of Cardiff's Dylan Lawlor offers some relief but the absence of Davies' calm leadership and unrivalled experience will undoubtedly dent Welsh confidence ahead of the play-off semi-final.