Giants backup catcher candidate: Tyler Heineman
Tyler Heineman was recently added to the team on a minor league deal. He is a switch-hitter and has been a minor league journeyman for most of his career. However, he did get his first taste of the big leagues with the Miami Marlins last season.
In Triple-A last year, where he spent a majority of his time, he hit .336/.400/.590 with 13 home runs and 38 RBI. That was in the Pacific Coast League, which is notorious for batters tearing the cover off the ball, but nonetheless those are still solid Triple-A numbers.
He will definitely have to outshine Garcia in spring training if he wants to make the big league roster, but in a long season, I would expect to see Heineman get some action in the MLB level at some point.