Hooker Rory Best has been ruled out of Ireland's opening November international against South Africa on Saturday with a calf strain.
The Ulster captain picked up the injury during training at Carton House last week and it has been slower to heal than expected.
It brings to 17 the number of internationals unavailable to coach Joe Schmidt for the game against the Springboks, with the Leinster duo of Seán Cronin and Richardt Strauss vying for the number two shirt.
South Africa-born Strauss made his debut against the Springboks when they were here last in 2012.
Best will remain with the Ireland squad where he is partaking in modified training.
Schmidt will name his team tomorrow.