Last updated on .From the section Irish Rugby

Sexton picked up a groin injury against France

World Cup quarter-final: Ireland v Argentina Venue: Millennium Stadium, Cardiff Date: Sunday 18 October Kick-off: 13:00 BST Coverage: Live on BBC Radio 5 live and BBC Radio Ulster, plus live text commentary on BBC website

Ireland may gamble on the fitness of fly-half Johnny Sexton for their World Cup quarter-final against Argentina.

Sexton limped off in the first half of Sunday's Pool D win over France with a groin injury and is doubtful for this Sunday's last-eight tie in Cardiff.

The Leinster playmaker is back running in training and will be given until Friday to prove his fitness.

Meanwhile Ireland have not yet ruled out an appeal against the one-week ban handed out to flanker Sean O'Brien.

The Irish camp received the written judgement on Thursday morning and have 48 hours to lodge any appeal.

O'Brien, named man of the match in the 24-9 win over France, received the ban for punching Pascal Pape.

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.

"Johnny did about three-and-a-half kilometres of running today, so that's a positive," said Feek.

"We're quietly confident and we'll see how he goes on Friday.

"When you start to accumulate a number of games in a row, in the Six Nations you usually get two matches and then a week off, while in November you get three but you can still mix it around.

"But here it's do-or-die type stuff, so there might be some allowances around a few things, especially with our medical staff and strength and conditioners, they've got a good feel on things as well."

O'Connell leaves Ireland team hotel on crutches

Ireland are without two of their first-choice back row, with Peter O'Mahony joining O'Connell in exiting the tournament, whileS O'Brien is suspended for the Argentina game.

In what would be a major pack reshuffle, Ulster powerhouse Iain Henderson could switch from the second row to blind-side flanker, with Donnacha Ryan instead partnering Devin Toner at lock.

Chris Henry is likely to replace the banned O'Brien at open-side flanker, with Jordi Murphy and Rhys Ruddock to contest the back-row berth on the bench.