It depends on how you look at things.
A speedy guy like Weise in the bottom 6 who hit's isn't what the team needs. The speed was a non factor and the hitting and scoring aren't more than what's already brought.
Before the trade look at the bottom 6 guys this team has.
Weise, Dalpe, Richardson,Sestito, Kassian, Booth, Welsh, Schroeder, Lain, Hansen.
If you're trading one of these guys who's it going to be that you can get a return for? Weise becomes redundant and he's a guy who's contract is up. What does Weise do that Sestito doesn't.
I don't think this team needs both Dalpe and Booth. That may get figured out in the off season though. I guess we see what Diaz does and we can make a call on a guy like Corrado. This move for Diaz could just be a sign that Corrado isn't ready to have a real role on this team yet.