Skipper Duffy has a calf problem while O'Halloran has a hamstring injury and both have undergone cryotherapy in Cork in the hope they will be first for the all-Ireland clash.
But Elwood, whose side is currently in fourth spot after an impressive start to the season, is adamant he will have no issues in blooding the youngsters should the pair fail to prove their fitness.
"Gavin has a haematoma in his calf and Tiernan is struggling with a hamstring injury, so hopefully they can make the Leinster game," said Elwood.
"They have both gone for cryotherapy in Co.Clare and we are just keeping out fingers crossed that they will make the game. We are going to give the guys every chance to prove their fitness.
"I'd like to show faith in the younger boys. We don't have too many options in the back, but I have no issue going down to the U20s. I have already spoken to Nigel Carolan this morning and told him we have a bit of a crisis. I have no issue going there at all."
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