Second rows James Ryan and Ryan Baird have been ruled out of Ireland's final Six Nations clash with Scotland at the Aviva Stadium on Saturday.
Their fellow Leinster locks Ross Molony and Joe McCarthy have been called in to train with Andy Farrell's squad as Ireland chase a first Triple Crown triumph since 2018.
Ryan came out much the worse in a second minute clash of heads with England's Charlie Ewels in Ireland's victory at Twickenham last Saturday and has returned to his province to be guided through the return to play protocols, but Ireland's pack leader may be stood down for a few weeks after failing his HIA at the weekend.
Baird, meanwhile, has suffered a back injury and will not be considered for the Test as Ireland hope to pile pressure on France on the final day of the championship.
If Grand Slam chasing France lose to England in Paris in the last game on Saturday (8pm Irish time), and Ireland draw or win against the Scots (4.45pm), that would be enough for Farrell's men to claim the Six Nations title.
Molony was involved in the Ireland squad before, when he was called into the summer series squad but didn't win a first cap, while former under-20 international McCarthy has been included for the first time following a strong start to his career with the province since his January debut.
Ulster trio Robert Baloucoune, Nick Timoney and Mike Lowry all return after playing in their province's victory over Leinster on Saturday night.
Farrell has some big selection choices to make this week after Ireland's scrum was dominated by the England forwards and, off the bench, Jack Conan and Rob Herring impressed as the men in green eventually saw off Eddie Jones' 14 men.
Ireland Squad for round five of the 2022 Guinness Six Nations Championships.
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