Strain rules Jonathan Sexton out of Scotland clash
A scan yesterday revealed the extent of the injury and while he is officially rated as 'doubtful' for the game in Murrayfield on February 24, it is almost certain he will not recover in time, with his place being taken by Ronan O'Gara.
O'Gara stepped up from the bench for his 127th international cap on Sunday and is the only credible option for Ireland as they seek to salvage their championship bid against a Scotland side resurgent after their win over Italy at the weekend.
Ulster's Paddy Jackson should just about hold off the claims of Ian Keatley and Ian Madigan to sit on the bench as understudy.
It has also been confirmed that Simon Zebo is definitely ruled out for the remainder of the Championship after fracturing the fifth metatarsal in his right foot.
Zebo underwent surgery on the injury yesterday, with an expected 8-10 week recovery period.
Mike McCarthy (right) is also likely to miss the Scotland game after straining the medial ligament in his right knee, while Brian O'Driscoll (right ankle) and Donnacha Ryan (back) will also see specialists this week for further review.
Neither are expected to miss the Scotland game, and the prognosis is also good on Rob Kearney (dead leg) and Sean O'Brien (hamstring).
Ireland's narrow depth of talent is certainly stretched to almost breaking point with three games remaining the championship. The players report back to camp in Carton House for training on Thursday before breaking up again until Sunday night.