Doncaster Knights captain Michael Hills faces a lengthy spell on the sidelines.
Hills was stretchered off with the hamstring injury in the friendly defeat at Newcastle Falcons.
Director of rugby Clive Griffiths said: “Whilst Saturday was certainly a very worthwhile exercise, and we blew some of the cobwebs away, the one obvious negative was the loss of Michael Hills.
“The injury isn’t quite a bad as we initially thought but he is still going to be out for a lengthy period of time; certainly well-beyond the start of the Championship season.”
Former Leicester Tigers and Samoa star Alesana Tuilagi is currently training with Knights and could feature against Canada on Saturday.