Ireland head coach Joe Schmidt has revealed Sean O'Brien suffered a suspected broken arm during the win over Argentina.
The Leinster forward, who was playing his first game for Ireland in almost a year following shoulder and knee trouble, suffered the injury in the second half of the 28-17 win making a tackle and was replaced by Dan Leavy
"Looks like Sean has broken his right arm," Schmidt told RTÉ.
"That's likely to keep him out of the game for a while. He's devastated, obviously. I thought he had a pretty good start to the game. He was his physical robust self."
Schmidt also revealed that Irish scrum-half Kieran Marmion suffered an ankle injury during the game but is expected to recover in time to face New Zealand next Saturday.
Marmion, Bundee Aki and Luke McGrath scored Ireland's tries as the Six Nations champions started their November campaign-proper with a win over the stubborn Pumas.
Wing Bautista Delguy crossed for Argentina, who edged ahead in the second-half through Nicolas Sanchez's third penalty, before Ireland battled back as Johnny Sexton finished with 13 points.