The Credit Agricole rider sustained the injury in a fall on Thursday's sixth stage between Vitre and Tours.

He finished the stage more than 20 minutes down on the leader, but x-rays afterwards revealed that he had broken bones.

"Surgery may be needed," Credit Agricole sporting director Roger Legeay admitted.

"It's a tough blow for him and the team, but Stuart should be fit again for the Olympics."

O'Grady, 26, won a stage in the 1998 Tour and wore the leader's yellow jersey for several days.

He was runner-up in last year's green points jersey and had been targeting same competition this year.

Last autumn the Australian was involved in a serious mugging incident near his French home in Toulouse.

The attack left him with a head injury and blood clots which disrupted his build-up to this season.

Nevertheless he still finished runner-up in January's Tour Down Under, a major international event in his home city of Adelaide, which he won in 1999.