Brown has had a nice two weeks since coming off the DL. He has hit 4 homers and stole 5 bases in that time, with a line of .262 / .328 / .525 over 68 PAs in May, which is when he came back from the DL. He had a nice little 5 game stretch from 5/21 to 5/26, with 3 HRs.
I don't think you can say every minor leaguer who has a hot streak is a no brainer replacement for a bench guy in the majors. FWIW, Bernie since 5/26, with his starts, has gone 7 for 20 with 2 homers. You call up Brown after his little hot streak, and send Bernie down, you miss that from Bernie.
I don't see how you can criticize what Bernie has done this week, and before that, Brown was hurt or just off the DL. Bernie's performance as a fill in starter recently is least of the team's problems.
Wil Rhymes, OTOH, has a substantial track record that establishes he has no power. Tracy's job is pop off the bench. Rhymes for Tracy does not fit the structure of the team.