Mauers power went down because he's an opposite field hitter and Target field is death to LF, not because of anything else. I don't want Mauer as a C going forward, I want him as a 1B, which would protect him from injuries and keep him on the field (a la Napoli). For a guy who will hit you 45-50 doubles a year, get on based at a clip of over .400, and play 1B everyday, 20mm isn't a bad contract.
Like I said, I'm not certain that he will be available, I just think its ridiculous to call him a certainty to not be available. I don't know if anyone will certainly be available this deadline other than maybe a Matt Garza type who is in the last year of his deal on a losing club. If the Sox offer the Twins a good deal in terms of prospects and eat most of his salary, I'm sure the Twins would at the very least negotiate. Whether a deal gets done or not, who knows.
He's not a guy I "mentally masturbate" over, like Bogaerts or Stanton, he is a guy who I think would fit in perfectly with the lineup and fill a huge void at 1B that we really have nobody in the minor leagues to fill. And in a couple years, after Ortiz leaves, he can split time at 1B/DH, as he gets older.
The good thing about Mauer is that he is an OBP machine, and that isn't something that tends to drop off significantly with age like power or speed. So he would still be a very effective player at the end of his deal if he was in a modified DH/1B role.