"A lot of people do not know this but Piazza has actually been one of the most valuable DEFENSIVE catchers over his career. He usually has an outstanding defensive catcher behind him, but usually the pitchers have around a half a run ERA lower with him behind the plate than the backup. From 1993 to 1997 he was noticeably more valuable behind the plate than Ivan Rodriguez. (Check Pitcher's era for both)
"This makes sense. Since what they call "defense" (throwing out base runners, fielding bunts, tagging out runner's etc...) for the catcher only amounts to 2-3% of what the catcher does. 97-98% of what a catchers does is handling the pitcher, placing the pitch, (catching the ball), adjusting for hitter's etc... At this Piazza must be among the best in baseball.
"Saying that Piazza is one of the best hitting catchers in baseball is like saying that Nolan Ryan is an above average strikeout pitcher or that Rickey Henderson is a pretty good base stealer. By far more dominant at the plate than any catcher, despite playing in one of the worst hitting parks in baseball. Clearly a more valuable player than Bench, Dickey, Berra or Rodriguez
"In OBS (on base plus slugging percentage) Piazza is by far ahead of all catchers at some point of his career. Also in league offensive winning percentage (In you had 9 Piazza's and an OK pitching staff how many games would you win,) he is by far ahead of any catcher.
"Comparable hitters to Piazza=JOE DIMAGGIO and STAN MUSIAL. Add 60 points in batting average and 100 points in slugging percentage to Dave Kingman you and get Ken Griffey, Jr. Add 60 points in batting average, 100 points in slugging to Bench and you get Piazza. Piazza has been a much better hitter than Griffey Jr. throughout his career. Also Ivan Rodriguez plays in a park that adds 10 points to his batting average, while Piazza has consistently played in parks that take 10 points off his batting average." -Steven Ferges