Sean O'Brien has been hit with a one-week ban for punching France's Pascal Pape, leaving Ireland without three pivotal pack leaders for Sunday's World Cup quarter-final with Argentina.
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Flanker O'Brien had a two-week suspension halved due to his remorse after a lengthy disciplinary hearing on Tuesday, further denting Ireland's pack after injuries to Paul O'Connell and Peter O'Mahony.
No sooner had Ireland come to terms with the end of captain O'Connell's World Cup and Test career due to a torn hamstring than head coach Joe Schmidt was hit with another blow.
Schmidt will now be forced into a major pack reshuffle against the Pumas, with Iain Henderson and Chris Henry expected to start in Cardiff on Sunday.
O'Brien hit Pape in the solar plexus in the first minute of Ireland's 24-9 victory over France on Sunday, with Les Bleus boss Philippe Saint-Andre later branding the incident an "assault".
A World Rugby statement read: "O'Brien admitted committing an act of foul play and therefore the independent judicial officer Terry Willis upheld the citing.
"With respect to the sanction, the Judicial Officer deemed the act of foul play merited a low-end entry point of two weeks. The judicial officer took into account compelling mitigating factors including O'Brien's conduct prior to and at the hearing, his remorse, good character and clean disciplinary record, and reduced the suspension to a period of one week."
