You know, Giddens might do a half decent job replacing Posey. By no means am I happy about Posey going, I've been arguing fervently with many of you about keeping him at all costs.
However, most scouting reports talk about his freakish athleticism, his ability to hit the three, has really long arms, and the enthusiasm he exudes when he plays. Sounds a little like Posey. Moreover, we're not asking him to come in carry the load. All he'd have to do would be come in, play tough defense, hit weakside open threes, and dive for loose balls.
Of course he won't get away with what Posey gets away with defensively because he's a rookie and I don't expect him to have all the intangibles, but compared to what is available on the free agent market, he might not be much worse than what is on the free agent market.