And while O'Driscoll has reassured his coach Joe Schmidt that the setback is nothing serious, the Leinster boss is a little more tentative in his early diagnosis.
"It was his other ankle, that's his good ankle. He has just assured me that it's fine. But he did that last time so you don't know," said Schmidt.
"What I can I tell you is he's one of the most mentally tough players that I've ever had anything to do with and it doesn't have to be fine for him to play.
"He's tough and experienced and knows his own body and what he can push through."
O'Driscoll, who is hoping to take his place on a fourth successive Lions tour this summer, carried on after the injury at the weekend but appeared to be in some discomfort in the closing stages of the 33-14 victory at the RDS.
Leinster won't know until later in the week whether he will be fit to face Exeter Chiefs at Sandy Park in their final European pool game, while Ireland will hope that he isn't ruled out of - or his preparation affected for - the Six Nations opener with Wales in Cardiff on February 2.