I think it's safe to say that he is not a drastically worse player than last year and that he has went through his typical April slump and now we're going to see more of the typical guy at the plate. His defense seems worse than ever though and I don't remember him being a "cold starter" with that.
Either way if we're in win now mode, it's hard to make a case for trading him as he does provide an offense against lefties that is very lacking even with him. If you wanna see things get ugly think about how poorly this team would flail against lefties without him.
Not to mention holding onto him until the trade deadline will allow him to build up more value most likely, so if we're struggling maybe a team looking ahead to next season will actually pay for him and think of giving him an extension offer if they have a black hole (see how bad the FA class is). Problem is I just don't know who actually will view him as a long term SS...