But O'Connell has recovered quicker than initially expected and could hand Munster a major boost by returning to action as they chase both Magners League and Amlin Challenge Cup glory.
"Paul O'Connell could yet play a part in Munster's season following further tests on his injured ankle," read a Munster statement.
"O'Connell had his injury reassessed in Dublin yesterday evening and the prediction is he could be back training in four weeks time.
"That of course would mean that if Munster were to progress to the final of either Amlin Challenge Cup or Magners League, O'Connell could be involved."
O'Connell toured New Zealand with the Lions in 2005, making five appearances, and then skippered the famous tourists on the 2009 trip to South Africa.