Ireland flanker Sean O'Brien is out of Sunday's Rugby World Cup quarter-final against Argentina after he was handed a one-week ban for striking Pascal Pape of France.
The back-row man is a key figure in the Ireland pack and was named man-of-the-match after their vital 24-9 win over the French, which meant they avoided New Zealand in the last eight.
However, at a lengthy disciplinary hearing on Tuesday, O'Brien admitted to hitting Pape in the solar plexus in the first minute of the match.
He had a two-week suspension halved to one week due to his remorse, but the news he will be absent on Sunday is another blow to an Ireland side already reeling from the news that captain Paul O'Connell's Test career is over due to a hamstring injury.
Peter O'Mahony is also injured, meaning Ireland will be without three pack leaders when they tackle the Pumas in Cardiff.
Head coach Joe Schmidt will now be forced into a major pack reshuffle, with Iain Henderson and Chris Henry expected to start, while Rhys Ruddock, who was added to the squad as a replacement for O'Mahony, may also feature.
There is also an injury doubt over fly-half Jonathan Sexton, who has an adductor problem.
O'Brien was cited on Monday for swinging his forearm into Pape's midriff in the first 30 seconds of Sunday's match.
World Rugby released a statement after Tuesday's hearing which 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."
O'Brien will be free to play in the semi-finals, should Ireland triumph at the Millennium Stadium on Sunday.
Argentina will be without centre Marcelo Bosch for the Ireland quarter-final after he was hit with a one-match ban for a dangerous tackle during Sunday's win over Namibia at Leicester City Stadium.
The 31-year-old has 48 hours to appeal against his suspension.