I realize Bird is probably not long for this Cs roster, but aren't we using all 15 roster spots right now? I also have some concern about the luxury tax, but the longer we wait to sign him, the less he will cost.
As for if Zeller would be an actual useful body on the Cs, I am going to lean toward no. Baynes should be back at some point and that should shuffle everybody back to their best positions. Theis and Williams should, in theory, be able to handle back-up big-man minutes, but it wouldn't be the end of the world to have a player who is familiar with Brad's system back on the bench. He is also not exactly demanding and does his job when called upon.