This week, the Boston Red Sox selected top pitching prospect Payton Tolle’s contract and added him to the 40-man roster – a move that prevents him from being eligible for the Rule 5 Draft this winter. While that was undoubtedly the right move for Boston, Tolle's roster spot came at the expense of leaving someone else exposed.
Any prospects who were signed at 18 or younger and have not been added to their club's 40-man roster within five seasons of their signing are at risk of getting snatched up by another team in the December Rule 5 Draft, which allows clubs without a full 40-man roster to select certain non-40-man roster players from other clubs.