Ireland's historic victory over New Zealand on Saturday came at a cost, with Jordi Murphy ruled out for up to nine months after suffering an anterior cruciate ligament injury.
Murphy scored Ireland's first try at Soldier Field in Chicago, but was taken off on a stretcher after 25 minutes.
Joe Schmidt's team went on to win 40-29, beating the All Blacks for the first time to end the world champions' record 18-match winning run.
But Leinster forward Murphy now faces a lengthy spell on the sidelines after it was confirmed he suffered a serious knee injury in the United States.
Ireland on Monday announced Niyi Adeolokun, Jack O'Donoghue, Darren Sweetnam, Dan Leavy, Tiernan O'Halloran and David Kilcoyne have been added to the squad ahead of the match against Canada in Dublin on Saturday.