Julien has had a miserable month, so has Kirilloff, Jeffers has fallen off quite a bit. That's baseball. Great players have slumps, but by the end of the year, things almost always balance out. It's super hard to be patient watching Julien take strike three almost once a game, but if/when it turns into a 15% walk rate with decreased strikeouts, it will be acceptable again.
It is the coaching staff and front office's job to determine if a player can cut it or whether they will never get to the point where they will be a trusted regular. So far, they are sticking with Julien, but I believe their patience is wavering a bit. I truly don't believe they want to cut bait on a single position player on the active roster. I would bet on a minor injury trip to the IL for someone before any of the current 13 are sent to the minors. Further, I think it puts Keirsey on the back burner despite a really good run hitting and perceived skill as an outfield defender.