I think timing has definitely played a part this season too.. he was on fire, it was extra base hits every other game, really comfortable at the plate, and got injured at the worst possible moment and out for two months. Since then he has done okay, but isn't tearing down walls like he did early in the year.
The timing of Winker getting injured and then Rowdy struggling at this point just didn't help him, but I can see two ways he gets with the club again.
1) He goes on fire again, with a 1.100 OPS in Nashville and gets the callup to be a regular DH if the Brewers aren't hitting by the end of August (i actually think Canha has been unfortunate BABIP wise and looked solid at the plate)
2) the Brewers have him for next year. if he finishes the season out strongly, with a .950 ish OPS and the Brewers offense is going well enough they don't want to waste their final usage of him (especially with Tellez coming back, would probably mean DFA-ing Santana), then they'll keep him there, keep working in the offseason, and have him start next season in the majors