Addition by subtraction is not a bad thing, even if we get nothing in return.
However, I do agree with you that the situation is not so bad we need to let him go for nothing. There is no one breathing down his neck to take his spot in the rotation, unlike the situation with Youk, where it really came down to, keep Youk and play him (when he was obviously miserable) or trade him and play Middlebrooks. What we got for Youk was an afterthought, really. He was traded to make room for Middlebrooks.