Ireland have included Ulster duo Chris Henry and Luke Marshall in their 29-man squad ahead of Sunday's clash with Scotland at Murrayfield.
Henry is included despite suffering a knee injury in Ulster's RaboDirect PRO12 win at home to Zebre. He will undergo a scan on Monday.
His team-mate Marshall suffered bruising to his thighs during the same game, but the injury was not enough to rule him out of inclusion in an Ireland Six Nations squad for the first time.
The back, who scored for the Ireland XV against Fiji in November, was unavailable for the opening weeks of the Championship with a finger injury.
In addition to Marshall, back-rower James Coughlan and second-rows Lewis Stevenson and Devin Toner come into the Irish squad as extra cover, after being involved in the early preparations for the Championship.
The panel could have extra players added to it after further medical reports and the final squad will assemble in Carton House in Maynooth on Monday.
Ireland squad: Rory Best, Darren Cave, Tom Court, Sean Cronin, James Coughlan, Keith Earls, Luke Fitzgerald, Declan Fitzpatrick, Craig Gilroy, Robbie Henshaw, Jamie Heaslip, Iain Henderson, Chris Henry, Paddy Jackson, Rob Kearney, David Kilcoyne, Luke Marshall, Fergus McFadden, Conor Murray, Sean O'Brien, Donncha O'Callaghan, Brian O'Driscoll, Ronan O'Gara, Peter O'Mahony, Eoin Reddan, Mike Ross, Donnacha Ryan, Lewis Stevenson, Devin Toner.