The 35-year-old suffered a hamstring injury in last weekend's defeat to Racing Metro at the Stade de France and confirmation that the strain is serious enough to keep him out of the visit of last season's Heineken Cup semi-finalists is a major blow for the province.
It will also cause major concern for Ireland coach Declan Kidney as he prepares for the visit of South Africa on November 10.
The former Lions captain missed the first six games of the season with knee and back problems, but after lasting for an hour against the Top 14 side he is free to face Michael Bradley's Edinburgh.
The Ireland pair have been out of action since coming off injured in defeat to Connacht three weeks ago and have played less than 80 minutes between them this season.
D'Arcy, who has a rib injury, took a part in training at UCD yesterday, but Kearney stayed on the sidelines and is rated a greater doubt ahead of the Pool 5 clash. Eoin Reddan and Jamie Hagan sat out training as a precaution, while Dave Kearney and Rhys Ruddock could return to the British and Irish Cup squad at the weekend.