Like SSR said, they can ask all they want but there's no chance they get a Castro talent for Upton. There's very, very few talents like Castro anyway (Harper and Trout and that's about it) and Castro is more valuable than Upton anyway (cheaper, more team control, no injury concerns). If they demand Castro, I'm asking for Upton and probably at least one of their elite pitching prospects (Bauer/Skaggs/etc). They don't have to get a Castro talent, we're just talking about the Cubs' ability to trade for him. There's a large gap between someone like Castro and someone like Garza + Brett Jackson. The problem is that the Cubs don't have anyone in that gap for the D'Backs (Rizzo could headline a deal, but I doubt the D'Backs would be interested considering they have Goldschmidt). A team like the Pirates could offer Taillon and Cole. The Red Sox could start with Middlebrooks. The Cubs don't really have anyone like that (again, besides Rizzo).