The Houston Astros' roster issues are well-documented. It is bad enough when you have roster deficiencies on both sides of the ball to address during the offseason, but having to do so with a full 40-man roster and having to purge players ahead of time adds a level of difficulty. While it sounded like Houston was going to chip away at the roster problem after moving on from Chas McCormick, apparently they were just getting started on Tuesday.
With the number of roster additions they probably want to make as well as protect their players from the Rule 5, Houston needed to clear several spots from their 40-man roster.