Ireland's Six Nations title defence suffered a blow on Monday when wing Mack Hansen was ruled out of the forthcoming tournament with a dislocated shoulder.
Hansen is due to undergo surgery after sustaining the injury during Connacht's United Rugby Championship clash against Munster on New Year's Day.
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"Mack Hansen (shoulder) will undergo surgery today for a dislocated shoulder and is expected to be unavailable for three to four months," Connacht said in a statement.
Hansen's injury is the latest setback for Ireland, coming just three days after veteran prop Dave Kilcoyne was sidelined for up to six months.
Munster's Kilcoyne, 35, also suffered a shoulder injury that needed surgery.
Six Nations champions Ireland kick off their campaign against France in Marseille on February 2.
Hansen, 25, has developed into a key player for Ireland head coach Andy Farrell, scoring nine tries in 21 Tests since making his debut in February 2022.
The former Brumby made the move from Australia after debuting for the Brumbies in 2018.
He will also miss Connacht's final two European Champions Cup pool games against Lyon and Bristol.
Connacht are yet to record a win in the competition after defeats to Saracens and Bordeaux.
