The 22-year-old suffered a pectoral tear in Sunday’s 29-18 win over France at BT Murrayfield and his absence will be a blow as the Scots look to record three consecutive victories in the championship for the first time since 1996.
It was also confirmed that No 8 David Denton, who was forced out of the previous win over Italy on the eve of the match in Rome with a groin injury, will also miss the trip to Ireland.
A Scotland team spokesperson said: “A scan at Spire Murrayfield Hospital (on Monday) confirmed the clinical suspicion that Gray had sustained a partial pectoral tear in Sunday’s win over France, and has subsequently been ruled out of this weekend’s game.
“The Scotland management also confirmed that back-row David Denton has returned to his club, Bath Rugby, where he will continue his rehabilitation from the groin injury sustained on the eve of the Italy match in Rome.”
Ryan Wilson and Josh Strauss have played No 8 in the past two games, while Tim Swinson has been covering lock on the bench and could replace Gray on Saturday, with either Glasgow’s Rob Harley or Edinburgh’s Ben Toolis drafted into the matchday squad.