However after linking up with his club teammates to begin his rehab O'Connell believes he could be in action at the shorter end of the prognosis.
Munster currently sit second in the RaboDirect PRO12 table but with just a five point advantage over fifth-placed Ulster.
And O'Connell wants to be back in action as soon as possible to lend a hand to both their domestic and European duties with Munster's last-eight Heineken Cup clash with Ulster on April 8.
"I started my rehab on Wednesday evening with the Munster physio Dave O'Sullivan," he said. "Earlier that day I was back in the gym doing upper body weights in the company of Alan Quinlan and Mike Prendergast. It was entertaining and a welcome distraction."
"Frustrating would be one word for it. Injuries are part and parcel of sport but any philosophical attitude tends to disappear, initially at least, when it happens to you.
"The prognosis is four to six weeks with the Ulster match in the Heineken Cup falling in the middle of that but I would be very hopeful to be back in time for that game."
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