Ireland may gamble on the fitness of fly-half Johnny Sexton for their quarter-final against Argentina.
Sexton limped off in the first half of their Pool D win over France with a groin injury and is doubtful for this weekend's last-eight tie in Cardiff.
The Leinster playmaker is back running intraining and will be given until Saturday to prove his fitness. With captain Paul O'Connell already ruled out, Ireland can ill afford to lose another inspirational leader.
Scrum coach Greg Feek conceded Ireland are reluctant to take on the Pumas without Sexton, and may be prepared to make "allowances" even if he is not fully fit.
Argentina have shone in the tournament, rebounding from pushing New Zealand all the way before going down 26-16 to hammering the rest of their pool opposition, racking up 22 tries. The strength of Los Pumas is traditionally the pack and it is no different this time around.
"The combinations Argentina have, have probably been together for a bit longer," Ireland assistant coach Greg Feek said when asked to compare the Pumas to France, beaten 24-9 by the Irish in their final pool game last weekend.
"There seems to be more of a collective around that, they're a little bit more used to each other.
"Argentina really know what they want to do, they stick to it and it's a really tough challenge.
