There may be other things contributing, but the issue is the roster (and the FO that built it).
Backups (or worse) playing every day (nearly):
Kepler, Galllo, Taylor
Backups getting regular time:
Solano, Castro
Superstars being less than a shadow of themselves (possibly not on the FO, but no idea what Rocco can do about it while they are not on the IL)::
CC, Buxton
Mistake, or just a massive slump?
Vazquez
Young "great hitter" not hitting:
AK
Given that the entire OF is made up of DFA candidates and backups, and CC and Buxton stink....I have no idea how many speeches Rocco can give....Perhaps he could lead better, he can certainly make better pinch hitting decisions. Perhaps a new hitting coach would help some....but really, it is the roster.
This is 90% on the FO, and if anyone needs to make changes and possibly be fired, it is them. 100%.