But just when it looked like the Limerick man would be fit to make his first appearance of the season for Munster, a reccurance of the back problem kept him out of action.
An IRFU statement confirmed that O'Connell would miss Ireland's opening Six Nations games against Italy and France, but O'Sullivan remains optimistic that the 28-year-old could feature before the tournament is over.
Speaking at the launch of the 2008 Six Nations in London, the Irish coach said: "I was talking to Paul on Tuesday night and there was a concern about a week ago that he may need an operation on a disc problem which he has had before.
"Had that operation taken place, he could have written off the Six Nations and he would have been targeting the summer tour.
"They have decided to hold back on the operation and they have given him a steroid injection which is another course of treatment for that injury. If that works he could be back sooner rather than later."
If O'Connell maintains his recovery rate, he could come into contention for the visit of Scotland to Croke Park on February 23.
O'Sullivan revealed: "He is responding well to that injection. If that stays on the current track, then he could be back playing in the next two to three weeks which could have him in contention for an appearance for us at the back end of the Six Nations.
"The one thing about these back injuries is that he was hopeful of playing against Wasps last weekend and that came unstuck for him. So fingers crossed."