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Sure looks to me like Alex Avila was the best-hitting catcher in the AL, and a major reason why a 104 OPS+ team rose to 110. [In the same way that Buster Posey pulled the Giants offense up a several notches in 2010.]
And Granderson was homegrown and then cashed in for other pieces.
Seattle hasn't had a homegrown bat make a significant contribution to the lineup (Seattle's lineup, that is, not Cleveland's) for more than a decade.