Nacewa suffered a haematoma while O'Driscoll sprained an ankle and adding to Schmidt's injury woes, Kevin McLaughlin lasted just 12 minutes before leaving the field with an elbow problem while Andrew Conway hurt his neck after a tackle on Simon Zebo.
Schmidt already has fitness concerns over Rob Kearney, Cian Healy, Isaac Boss and skipper Leo Cullen but he's hoping for some positive news as the week progresses.
"Right now the biggest concern for us is injury," he said. "For me the frustration is that there is a lot of wait and see at the moment.
"It's great to get in on a Monday and say these are the plays I want, these guys to run in the positions. But when you're not sure who you have Monday and Tuesday means that when you're looking for clarity and continuity it just compromises the preparation a bit."
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