While watching Tim Lincecum's first start of the season, it was nearly impossible not to notice his battery mate, Hector Sanchez, flailing about behind the plate like Roberto Luongo trying to stop an unexpected wrist shot. Sam Miller of Baseball Prospectus considered the effect Sanchez's defensive deficiencies may have on the performance of Giants' pitchers:
Sanchez is a young catcher who can theoretically hit but who struggles with some of the more nuanced parts of the game, such as framing. In 56 games last year, Sanchez gave back eight runs on framing alone; apply those runs to his WARP and the Giants' replacement level backup turns into a very questionable major leaguer, for now at least.
In an attempt to gain some insight into how much worse Giants pitchers had it with Sanchez behind the plate, I took a quick glace at the 2012 CERA's of the Giants' catchers. (via ESPN)
As you can see, pitchers surrendered about a half run more with Hector Sanchez behind the plate as opposed to Buster Posey. However, using CERA can only provide a very crude picture of how a catcher affected pitcher performance, if at all.
A few years ago, Keith Woolner performed an extensive study to determine if there was any statistical reason to believe that catchers impacted pitcher performance and found that any effect is almost certainly undetectable given the sample size we have to work with.
It seems important to note that Sanchez caught Tim Lincecum on 17 occasions in 2012, and Lincecum struggled his way to a 4.18 FIP. It's nearly impossible to determine how much of Lincecum's struggles were influenced by Hector Sanchez's catching deficiencies, but looking at charts like the one below (assembled by Sam Miller using data from Brooks Baseball), doesn't help Hector Sanchez's case much. Sam conveniently circled the pitches in the strike zone that were called balls.
One could reasonably assume that a pitcher knows to a certain degree what a strike looks like and would be fairly discouraged when their catcher causes the pitch to be called a ball. It will also cause the pitcher to throw more pitches than should have been necessary.
It is tough to assign a hard value to how much Hector Sanchez's catching harms pitchers, but it seems that the Giants would be better off not using him behind the plate very often.
All stats courtesy of our friends at FanGraphs unless otherwise noted.