Ireland have suffered a blow ahead of this afternoon's Six Nations opener against Wales as Jamison Gibson-Park is ruled out.
The vastly experienced Conor Murray will start at scrum-half instead at the Principality Stadium (2.15pm).
However much of Ireland's high-tempo game is based around Gibson-Park's rapid delivery and so Andy Farrell's side week will have to re-adjust to the late change.
Murray, 33, found himself out of favour at Munster in recent weeks but starts here ahead of his provincial colleague rang Casey, who is promoted to bench duties.
The loss of Gibson-Park came after he took part in yesterday's Captains Run at the stadium and the IRFU are yet to confirm the reason for his withdrawal.
It is another set-back after Tadhg Furlong was ruled out towards the end of the week as he was not quite ready to return after a calf injury.
The absence of Gibson-Park and Furlong makes Ireland's mission to win a first Six Nations game in Cardiff in a decade more difficult.
But Farrell has put an emphasis with his players overcoming unexpected changes and will demand that the late withdrawal does not affect Ireland's bid to build winning momentum at the start of this World Cup year.
Cian Healy will also miss out on the game through injury with David Kilcoyne replacing the Leinster man on the bench.
Healy was named on the official team-sheet distributed at the ground this afternoon but is the latest big name to withdraw
Munster veteran Kilcoyne has been in fine form for the province in recent times and has been rewarded with a call up to the bench in Healy's absence.
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