Tadhg Furlong and Iain Henderson face a race against time to prove their fitness for Ireland's Six Nations clash against Wales.
Lock James Ryan has been passed fit after a groin issue, so will be free to contest selection for the weekend's Dublin battle.
But tighthead prop Furlong and second-rower Henderson are yet to prove their fitness after hamstring complaints.
Defence coach Andy Farrell admitted Ireland boss Joe Schmidt could even wait until Thursday morning before finalising his line-up, as Furlong and Henderson fight for fitness.
"Tadhg is hitting his markers and he's training well," the Ireland assistant said.
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"He's not been in full training, he's been doing a bit-part of stuff and we'll make a decision on that Wednesday night, Thursday.
"Ian Henderson, a bit like Tadhg, is hitting his markers and pushing in the right direction. We'll assess how he pulls up after two hard days of training.
"There's not a risk, we wouldn't take risks. We back the squad that we've got, the full squad we've got, we've got quality players across the board.
"We'll make the right decisions come Wednesday or Thursday."
Ireland's meticulous boss Schmidt would normally demand his players prove their fitness on the Tuesday of a Test week building to a Saturday match.
He has bent on that strategy in the past however, and so may well hand British and Irish Lions duo Furlong and Henderson further time to prove their readiness for battle.
