Leinster's European Cup winning captain Leo Cullen is set to play his first Six Nations match in seven years after lock Donncha O'Callaghan was ruled out of Ireland's team to play Italy in their tournament opener against Italy here on Saturday.

O'Callaghan failed to pass a fitness test on his injured left knee on Wednesday and Ireland, the reigning grand slam champions, called the 32-year-old Cullen - who captained Leinster to European success in a thrilling final over former club Leicester last year - into their starting line-up on Thursday.

Now the experienced Leinster lock, as he did against Fiji in November, will take O'Callaghan's place in the second row alongside British and Irish Lions skipper Paul O'Connell.

This weekend's game will be Cullen's first Six Nations match since he started against Wales in March 2003.

Munster's Donnacha Ryan has taken Cullen's bench place and will make his first Six Nations appearance if he comes on at Croke Park.

O'Callaghan's withdrawal came after fly-half Jonathan Sexton, who kicked all of Ireland's points in their 15-10 win over world champions South Africa in November, was forced out with a dead leg injury.

Ireland will also be without back-row forward Stephen Ferris because of a knee problem.

Ireland defence coach Les Kiss said he anticipated O'Callaghan being fit in time for the match away to France a week on Saturday.

"I think it's about five years since he missed a game so it's tough for him. He's done all he can to be ready but it's not to be," Kiss told RTE.ie.

"We're aiming for France obviously. The rehab the medics have done over the last 10 days has been phenomenal - it's come on fantastically. He'll be thereabouts."

Revised Ireland team to play Italy in a Six Nations international at Croke Park here on Saturday 1430GMT (Sunday 0130 AEST)

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Rob Kearney; Tommy Bowe, Brian O'Driscoll (capt), Gordan D'Arcy, Andrew Trimble; Ronan O'Gara, Tomas O'Leary; Jamie Heaslip, David Wallace, Kevin McLaughlin, Paul O'Connell, Leo Cullen; John Hayes, Jerry Flannery, Cian Healy

Replacements: Rory Best, Tom Court, Donnacha Ryan, Sean O'Brien, Eoin Reddan, Paddy Wallace, Keith Earls

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