The only answer I can come up with is the team doesn't for a second believe the bogus hype about Castro's defense. Gonzalez isn't going to hit, at least not enough to make a positive difference. No one's signing that guy for his bat. His calling card is his defense and if the Reds are signing him, then it's a pretty clear signal they covet his defense and that they don't think Castro can provide it.
My belief has been that Castro was never going to get more then 150 ab's, he's more a mentor, but we've covered that already.
5 million for the SS a million each for the 3rd baseman and the 2nd baseman and then throw in Hattebergs low salary and there's your pickin' infield with range, speed and some EBH pop for about what Milton makes.