Since then he has taken a back seat and watched on as Ireland have impressed in the early stages of the tournament.
And O'Donnell, who made 13 GUINNESS PRO12 appearances last season, says he's taken the positives out of his enforced lay-off.
"If it was a much more short-term injury where I would return two weeks after the World Cup ended I think I'd be watching every game and playing it out," he said.
"But I've taken a back seat and become a real supporter and I have really enjoyed watching every game possible, enjoying both the spectacle and atmosphere of it."
To buy tickets for the GUINNESS PRO12 Grand Final click here. Also follow us on Facebook, join the conversation on Twitter, sign up to our YouTube channel for extensive match highlights and sign up for our newsletter for regular updates on the GUINNESS PRO12.