Every year, there is a deadline to add baseball players to an organization’s 40-man roster. This is often termed as a “40-man roster crunch” because, due to the nature of the Rule 5 draft, there are generally more players to be added to the 40-man roster than there are available.
See, the Rule 5 draft is intended to prevent teams from stockpiling minor league talent and withholding promotions via giving teams an opportunity to draft certain qualifying minor leaguers from other organizations—unless those players are on the 40-man roster. The result is that teams with the most talent end up with the biggest roster crunches, because not only do they have the most talent on their big league roster, but they also have the most talent in their farm system.