I've made my feelings on Matt Wallner known before. Happy to see him succeed, but I do think the Twins need to have a 4th OF that is able to hit lefties decent enough in the event that Wallner's inability to hit LHP persists. I do think a likely situation is the 4th OF having to share duties with Wallner in RF next season.
This is a bit of a concern since our starting CF is also someone we know has to have a competent backup since he can't be expected to play 75 games in the field. Both of these players needing a planned competent backup is a huge burden on the front office in terms of roster construction.
Castro can fill in, but an actual 4th OF is needed. Because much like this season, I'd expect them to get as many, if not more, starts as the starting 3. Case in point, useless 4th OF Margot is tied for the lead in OF appearances the next time he comes in. How pathetic is that?