Munster's Alan Quinlan is at openside flanker with Simon Easterby coming back at blindside wing-forward, while Victor Costello moves to number eight in place of the injured Anthony Foley.
The rest of the first-choice side, including Paul O'Connell, is as expected with David Humphreys retained in the playmaker's position. O'Sullivan, however, revealed that he agonised over the Humphreys/O'Gara dilemma once again:
"There was a huge amount of debate about that. At the moment David is in the driving seat, just by the skin of his teeth really, but over the two games it could have gone either way."
Keith Wood captains the side for the 34th time in 56 Test appearances.
* Ireland's record against Argentina is Played 5, Won 3, Drawn 0, Lost 2, Points for 115, Points Against 111.
The Ireland team to play Argentina is:
15 - Girvan Dempsey (Leinster - Terenure College); 14 - Shane Horgan (Leinster - Lansdowne), 13 - Brian O'Driscoll (Leinster - Blackrock College), 12 - Kevin Maggs (Bath), 11 - Denis Hickie (Leinster - St. Mary's College); 10 - David Humphreys (Ulster - Dungannon), 9 - Peter Stringer (Munster - Shannon);
1 - Reggie Corrigan (Leinster - Greystones), 2 - Keith Wood (Munster - Garryowen) Captain, 3 - John Hayes (Munster - Shannon), 4 - Malcolm O'Kelly (Leinster - St. Mary's College), 5 - Paul O'Connell (Munster - Young Munster), 6 - Simon Easterby (Llanelli), 7 - Alan Quinlan (Munster - Shannon), 8 - Victor Costello (Leinster - St. Mary's College).
Replacements: 16 - Shane Byrne (Leinster - Blackrock College), 17 - Marcus Horan (Munster - Shannon), 18 - Donncha O'Callaghan (Munster - Cork Constitution), 19 - Eric Miller (Leinster - Terenure College), 20 - Guy Easterby (Rotherham), 21 - Ronan O'Gara (Munster - Cork Constitution), 22 - John Kelly (Munster - Cork Constitution).