Safe
The Royals traded for both of these pitchers after they were selected in the Rule 5 Draft. Because of this, they need to stay on the major league roster the entire season or be returned to their former teams. In a rebuilding year, neither will likely be cut in Spring Training. Keller has more of a chance long-term at becoming a back-end starter, while Smith has a big fastball that should be useful coming out of the pen. If both can hold their own against major-league hitters, they should be able to hang on for the duration of the season.
It would be an absolute stunner if Jesse Hahn did not break camp with the Royals. In a perfect world, he would actually break camp as the fifth starter by bumping out Jason Hammel. With that scenario unlikely, Hahn should take over the Chris Young swingman role for the 2018 Kansas City Royals. He will be the first man up if (when) a starter goes down with an injury.
Until then, he will chew up a couple of innings here and there to give the rest of the bullpen a rest. Hahn still possesses big potential and has battled injuries for much of his career. If he can stay healthy and claim a spot in the rotation, the Royals will have easily won the Brandon Moss trade.