Despite leading for most of the game, Ireland went down 22-20 with Leinster's Felipe Contepomi angling over the match-winning drop goal for the hosts. But there were plenty of plusses for the tourists - Munster winger Brian Carney marked his debut with an early intercept try, and Jerry Flannery and Jamie Heaslip were among a number of forwards to impress.
A second half penalty try from a strong Irish maul helped O'Sullivan's side go 17-9 in front, but a loss of discipline cost them position and points, allowing Argentina back into the game and to stay in touch.
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