O'Callaghan sidelined by knee injury

Ireland lock Donncha O'Callaghan has withdrawn from Saturday's RBS 6 Nations opener against Italy because of a knee injury.

O'Callaghan's place in the starting line-up is taken by Leo Cullen of Leinster, who is promoted from the bench.

Munster forward Donnacha Ryan, who has won three caps, fills Cullen's place among the substitutes.

O'Callaghan has been struggling with the injury sustained on Heineken Cup duty against Northampton two weeks ago.

The 30-year-old, capped 58 times and a veteran of four Lions Tests, was included in the team on Tuesday only to be ruled out after undergoing a fitness test on Wednesday.

O'Callaghan is the third player made unavailable for the tournament opener because of injury with Jonathan Sexton and Stephen Ferris suffering from a dead leg and knee problem respectively.

Ireland defence coach Les Kiss expects O'Callaghan to be available for the crucial trip to France on Saturday week.

"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 it 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."

While the loss of O'Callaghan is a significant blow, Cullen is a capable deputy. The 32-year-old has 20 caps and led Leinster to Heineken Cup glory last season, though Saturday will be his first Six Nations appearance since March 2003.