Mike Ross could miss Ireland's Six Nations opener against Wales on Sunday 7 February after suffering a serious hamstring tear in Leinster's Champions Cup defeat by Toulon at the weekend.
Leinster have indicated that the prop faces six weeks on the sidelines due to a "high grade" hamstring strain.
Ross, 36, has started all of Ireland's Six Nations matches since making his debut against Italy in February 2011.
That amounts to 25 consecutive appearances in the number three jersey.
His absence could open the door for Nathan White, Tadhg Furlong or Marty Moore to start at tighthead against Wales in Dublin.
Ireland coach Joe Schmidt already faces the prospect of starting his side's defence of their Six Nations title without Peter O'Mahony, Iain Henderson and Tommy Bowe, as well as retired captain Paul O'Connell.
On a more positive note for the Irish coach, Leinster flanker Sean O'Brien could come back into the frame for Sunday's clash with Munster after being out of action since the 15 November defeat to Wasps because of an inner ear problem.
Fly-half Johnny Sexton is a doubt for the Irish interprovincial derby after suffering a recurrence of the quad muscle injury which ended his involvement in the World Cup.
Meanwhile Cian Healy will have his appeal against a two-week ban handed out for dangerous play heard on Wednesday.