Aaron Ramsey has left the Wales squad and returned to Arsenal for treatment on a thigh injury.
The 28-year-old will play no part in Wales' opening Euro 2020 qualifier against Slovakia in Cardiff on Sunday and will now have to prove his fitness before Arsenal return to Premier League action against Newcastle on April 1.
"Aaron's gone back to Arsenal," Wales head coach Ryan Giggs said. "He's not available tomorrow.
"His injury didn't clear up in time so it's obviously a blow.
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"He was in good form but it gives a chance for someone else."
Wales had previously been optimistic that Ramsey, who had missed a 1-0 friendly win over Trinidad and Tobago earlier this week, might be able to play some part in the match against Slovakia but the Arsenal midfielder has not recovered in time.
However the Welsh camp were optimistic that it was a relatively minor blow to Ramsey and it appears unlikely that would had initially been termed a "slight knock" will sideline him for much of the run-in.
The injury is certainly problematic for Giggs, who says he is working on a "Plan B" in the absence of one of his most important players. However Wales are set to welcome Gareth Bale and Ben Davies back into their side for the game against Slovakia.
Ramsey, who is set to join Juventus on a free transfer this summer, has flourished in recent weeks in Unai Emery's 3-4-1-2, showing impressive defensive discipline alongside Granit Xhaka.
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