Kepler (I think) is now only a right fielder, much like Buxton is only a DH. Kepler and his mediocre offense and good defense, is a roster problem. He’s a major league veteran with a lot of time on this team, but it sure looks like his time is almost up.
It’s easy enough to say “send him to center field” or use him as a fourth outfielder, but I doubt it’s that easy in practice.
Wallner and Julien (and Castro) have all shown ability and also made misplays that cost the team. The experienced players that could/will supplant them most likely make fewer mistakes, but maybe don’t add production that these guys might provide.
It’s far better to have the likes of Julien, Lewis, Wallner and maybe Miranda ready to step in than a bunch of AAAA players.