The notoriously conservative coach Declan Kidney simply could not ignore the hat-trick of tries against Fiji, coupled with the improvements delivered this season, particularly in his work under the high ball.
Twenty one-year- old Gilroy is the only change to the side which was overtaken in a second-half power play by South Africa two Saturdays ago, replacing Andrew Trimble.
This follows quickly on from the announcement that Gilroy has signed on the dotted line of a three-year contract extension at Ulster.
The primary playmaker Jonathan Sexton has recovered from a worrying groin strain that forced him away from the bench against Fiji last Saturday.
Leinster’s Gordon D’Arcy and Munster’s Keith Earls have held off claims made by the impressive Ulster centre partnership of Luke Marshall and Darren Cave.
IRELAND (v Argentina): S Zebo; T Bowe, K Earls, G D’Arcy, C Gilroy; J Sexton, C Murray; C Healy, R Strauss, M Ross, M McCarthy, D Ryan, P O’Mahony, C Henry, J Heaslip (capt).