Something has become abundantly clear: there is no longer space for Derrick Turnbow on the Milwaukee Brewers roster. Don't get me wrong, he's not all bad. He is capable of being very dominant at times, and can convert leads at a reasonable rate. He can surely be put to use as a setup man on a good number of major league teams.
The problem is that manager Ned Yost clearly does not trust Turnbow to pitch in close games. Until Monday, Yost had yet to put him in a situation where the team was tied or ahead, though he could have done so literally dozens of times. He was right here, because it seems clear to me that David Riske, Salomon Torres, Guillermo Mota and Brain Shouse are all better options than Turnbow on any given day, at least at this point. Given his history, there is a good chance that this situation where Turnbow is well down the pecking order at any given time is likely to persist.
Not every pitcher in the pen needs to be able to be trusted in tough situations. There is room for a mop up guy, even in a good pen. The thing about being a mop up guy for a good team is that he needs to be able to soak up innings on the comparatively rare occasion when he is called on. Turnbow is simply not capable of doing this. This leaves him in no mans land and unable to pitch his share of innings for the team. As a result, other pitchers in the pen will have to be overworked to compensate for his lack of usage. As was noted here, that has already begun to happen.
A contending team will play a lot of close games. The Brewers need to put in pitchers it is reasonably certain it can trust in these games. If a pitcher cannot be trusted in those situations, he needs to eat big chunks of innings in games that are not particularly close to take the pressure off the rest of the pen. Turnbow is not capable of the latter and cannot be trusted to do the former. Thus, there is no longer a role for him on the Milwaukee Brewers.