Ireland coach Joe Schmidt says Dave Kearney and Sean O'Brien are likely to miss the rest of the Six Nations.
Both men damaged their hamstrings last weekend in the one point loss to France.
In further bad news Mike Mc Carthy has been ruled out for the rest of the season.
Ireland's Mike McCarthy down injured in the France match ©INPHO/Dan Sheridan
Johnny Sexton rolled on his ankle at today's training session in Mullingar but the coach says he will be back in training next week.
"He just rolled his ankle. He could have trained on but we sent him to the side. He rolled and he did all the initial stuff in the unit split but in the end, most of what we were going to do was broken play work and so we didn't really need him in there," he said, adding that "Johnny will be fit to train on Monday".
Ireland's next game is against England at Twickenham next Saturday.