Ben Davies is out of Wales' Euro 2016 qualifier against Belgium on 12 June after having surgery on a dislocated shoulder.
The Tottenham defender slipped and fell awkwardly during the Premier League match away to Southampton on Saturday.
The 22-year-old full-back had an operation on Wednesday and will miss the rest of Spurs' league campaign.
But Real Madrid forward Gareth Bale has returned to full training after being sidelined by a calf injury.
Davies, who has 13 Wales caps, tweeted from his hospital bed: "Op went well and now on the mend. Thanks for all your kind messages."
Wales boss Chris Coleman has a ready-made option on the left of defence in Swansea City's Neil Taylor.
Belgium's 1-0 win in Israel saw them replace Wales as Group B leaders on goal difference and both sides will go into the game at Cardiff City Stadium unbeaten after five qualifying games so far.
Wales coach Osian Roberts has said he has no concerns over Bale's recent injury being a long-term problem.
Midfielder Andy King, who missed Wales' last two qualifiers because of suspension, limped off during the first half of Leicester City's defeat by Chelsea.