That was their last effort to be competitive and finally announced the rebuild.
Remember they started off something like 25-10 and Matt Latos imploded so as usual, Jerry tried to be competitive.
Sure would be nice to have him but Anderson came up at the same time of the trade. It's not like Jerry Dybzinski's holding down short.
Everything you say here is accurate. I would argue that if they wanted to be competitive, maybe trade Tatis for someone better because Shields was hot garbage when they got him. They didn't know that, though, but they should have. San Diego couldn't wait to get him out the door and even picked up some of the money as I recall.
https://blogs.fangraphs.com/james-shields-has-been-messed-up-for-a-while/
Still, bad. The way this team is being run at present, they don't do that move and they figure out a way to have both guys. Anderson was a draft pick, Tatis was an International Free Agent. Inferring based on what I know of Mr. Williams, he saw more value in one guy than the other because he was a draft pick.
Didn't like the move then, don't like it now. Even with a six year age difference, if these two guys stay healthy, I'll put my money on Tatis having the better career when all is said and done. Playing in a pitcher's park 81 times a year versus Anderson playing in a hitter's park. Also a bad reason to get Shields.