Why? Just because you take a pick doesn't mean you're married to the guy for 162 games. You can always return them. Guys get injured, especially Mata. Also, they probably want to SEE Mata in ST. Just making a pick in Rule 5 costs virtually nothing. They have open 40 man spots to do so. They also have open AA and AAA spots for the MiLB portion if the Cubs, Giants, Twins or Other left guys available that Breslow/Bailey/Willard/et al like.