Hooker Duncan Casey and wing Simon Zebo sat out the contact sessions in training on Tuesday, while captain Peter O'Mahony began rehabilitation following his hip injury with some running sessions.
Foley said: "We will know more on Thursday across the three of them.
"Peter is the captain of the side and we all want him to get there, but if it is not right for him to get there he will not be taking the field.
"It is important that we look after the lad as well but we will give him every opportunity to get in for the semi-final because he is a big player, he is one of our internationals.
"With Simon he didn't do contact, he will do it on Thursday. He is a lot fresher. Obviously the back spasms have calmed down, he was moving pretty free, and hopefully we just need to finish off his return to play protocols, which will involve a certain amount of contact on Thursday."
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