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In rotisserie, it's axiomatic that if you take a pull from the LF player pool, you're going to get a whale of a lot more offense than you will with your pull from the C player pool. But as you say, individual MLB orgs don't take pulls from pools of 30 major league catchers. They've got what they've got -- Adam Moore at catcher, or Mike Zunino at catcher.
For SURE, replacement level varies wildly according to the island of talent that a team is standing on.