Catcher is fairly similar. Some of the stat freaks looked at MLB catchers. They wanted to see what was the minimum batting average for a great defensive catcher compared to a great hitting catcher. They decided that even with a batting average of .000, the great defensive catcher is more valuable. Just framing the pitches well can be worth > 1 run per game, and the best hitting catchers aren't worth > 1 run per game on average.
Ivan Rodriguez - even if he'd batted .000 - would be more valuable than Mike Piazza?