"I had managed good contact in a tackle on James Hook and was in a position to get back to my feet quickly and contest for the ball. Lee Byrne came in an lifted one of my legs and this was followed a split second later by bodies hitting the ruck," O'Driscoll explained.
"I took all the force down my standing leg and knew straight away that I had torn the hamstring. Having suffered a few in my time I am now quite an authority on the subject.
"I have been trying to change my technique when it comes to grappling for ball at ruck time but the pop I heard told me that I'll have to keep working on it.
"I hobbled back into the defensive line because the ball didn't go out of play for ages and I was praying that nothing would come my way. It was a little after 5pm when I got a taxi from the hospital back to the team hotel."
O'Driscoll was replaced by his Leinster colleague Luke Fitzgerald in the 71st-minute and explained how he will be stepping up his rehabilitation work next week after a few days of rest.
"The pain had eased a little and there was more movement on the Sunday and still more on the Monday so I knew it wasn't as bad as first feared," he admitted.
"I went for a scan on the hamstring and it was confirmed that I would only be out for three or four weeks. I'm going to take a few days off and just relax before getting into serious rehabilitation next week. I won't be travelling to London with the boys because it wouldn't be conducive to the recovery process for the injury.
"The way it happened to me was just accidental and that is some comfort given the fact that once again I am destined not to compete a Six Nations championship injury free."
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