In previous seasons, Texas has added a number of amateur tryout players to the roster as the playoff race has heated up. Many of these were draft picks who finished their seasons like Brenden Dillon and Jack Campbell. Others include undrafted players like Derek Hulak. While I can't account for the undrafted players that Texas may have its eye on, the drafted or signed player pool is rather limited right now for the Stars. Many of the players drafted in the past few years went without a contract. Alex Peters and Brent Moran are two examples.
Last season, I did a story on the Stars' ATO tradition that may help you understand the process better.