A number of players are expected to be released on Tuesday from the international training camp in Limerick to their provinces for the latest round of Magners League fixtures, but may not be available for training until Wednesday.
But Schmidt insists the uncertainty makes preparations considerably more difficult, especially as Edinburgh have already beaten them this season and are expected to have all their Scottish internationals available.
"It makes preparation for this weekend relatively difficult. I think there's a couple we can maybe guess at, but it's crazy to get because we're not absolutely sure," said Schmidt.
"They might want to give more game-time to some. Jonny Sexton has only had three games, so is that enough to have him in top shape?
"I'm not sure. There are other guys, like Luke Fitzgerald, who took a bit of a knock but could have played for us last week. I don't know really what their thoughts are, as far as those kind of guys are concerned.
"We'd just got some continuity in selection and in the way we were playing, so the frustration is not so much that we're going to have a lot of new guys and a lot of young guys playing, just that we have to sort of get that cohesion again - that's really important, obviously."