I honestly don't have a great recall of who all the backups around the league are at the moment. I asked the question because my understanding is that most backups are (1) guys that have never started a game, e.g., Tolzien or Mallet, or (2) guys who are even more washed up than Sanchez, e.g. Campbell.
This last year was Sanchez's worst by far. Before that, he was never considered elite but he was considered a serviceable starter in some circles. A youngish guy with championship experience and decent stretches of production makes an above average backup in my mind.
Also to clarify, I'm not discussing this from the 49ers perspective. Don't want him. Just curious which teams right now have the most "solid" backup QBs, and I think a released Sanchez could easily latch on somewhere where he would be considered a decent fallback option in the event of catastrophic injury.
As far as the 49ers, I'm still waiting for the Raiders to inevitably give up and release Pryor so Harbaugh can get his hands on him.