The Rangers' attempt to keep Rule 5 pitcher Fabio Castro on the roster has come to an end. Forced to make room for pitcher Robinson Tejeda, the Rangers designated Castro for assignment before Saturday's game with the Colorado Rockies. The Rangers are working on a possible trade rather than having to return Castro to the Chicago White Sox. "We think there's a good chance we'll be able to find him a home in the Major Leagues," Rangers assistant general manager Thad Levine said. "That's our commitment to him, to put him in a similar situation that he had here. Based on what he did in Spring Training and with his Major League opportunity, we're getting interest."