I think you have to be careful about overpaying for a career year in Castro's case, especially since he was awful last year. The Cubs just got a prospect of comparable value to Syndegaard for two starting pitchers, one of whom (Samardzija) is more valuable than Castro right now. Having said that, Castro is 24, his career norm is an improvement over what we've got, his contract is lengthy but not burdensome, and he could probably switch to second and do just fine if you don't like his glove at short (which has been consistently below average but not brutally so). I wouldn't go all in for him, but I'd talk to the Cubs for sure.