November 20th was the deadline to place Rule 5 Draft eligible players on the 40-man roster or risk losing them. Rule 5 deals with players who have either four or five years with a club but haven’t been placed on the 40-man. At this point, clubs must protect them by placing them on the 40-man or expose them to the Rule 5 Draft at the upcoming Winter Meetings.
The four-our-five year specification is explained HERE.
Baseball America has a comprehensive rundown of who got added to their clubs’ 40-man roster today and thus are now protected.