Not to mention Chourio didn't have all that much time in A+. There was debate on where the Brewers were going to place Chourio this year and I think most had him starting in A+ and not in AA. The assignment of Chourio was very aggressive by the Brewers. MLB is also experimenting with baseballs in AA this year I believe which maybe causing some issues here.
I think Chourio, Quero, Black and Misiorowski are probably the only untouchables in the Brewers minor league system. I think the Brewers are willing to part with Frelick if it means an impact player is coming back to them with 3-4 years of control. Something similar to a Yelich type of a trade.