The Giants have scored the fewest runs in baseball in part due to Buster Posey's season-ending injury, so it's not surprising that both Ken Rosenthal and Jon Paul Morosi of FOX Sports are reporting that a catcher upgrade is the team's focus right now. They've specifically shown interest in Rangers' backstop Yorvit Torrealba, who started his career in San Francisco.
There are two significant roadblocks to a deal according to the FOX scribes. First, Texas can not seriously consider moving Torrealba until Mike Napoli comes off the disabled list, at the very least. Secondly, the Giants are reluctant to pay the $3.25MM he's owned next season. The Rangers would want a bullpen arm in return, but San Francisco is hesitant to part with any of their relievers other than Guillermo Mota.
Rosenthal and Morosi say that Ivan Rodriguez, Ronny Paulino, and Ramon Hernandez have also been discussed internally by the Giants. The Reds are unikely to part with Hernandez even though Ryan Hanigan gets the majority of the playing time behind the plate.