Who will pass the Zorilla test?

Anyone care to guess who will be the most underappreciated player in the majors in 2009? I know what you're saying ... "Rob Neyer, how could we ever measure such an amorphous thing?"
Easy, Dear Readers: by comparing performance to MVP balloting. And if you listen to some people -- or rather, if you listen to some ways of measuring performance -- few players will be more underrated than Ben Zobrist. Jonah Keri, take it away:

    The AL MVP debate that launched a thousand blog posts ended long ago. Other than Mark Teixeira's mom, South Bronx Vinny ("Hey Mike, first time, long time") and sportswriters whose baseball learning curve peaked in Cap Anson's prime, everyone's ready to hand the hardware to Joe Mauer.
    Mauer led the AL in batting average, on-base percentage, slugging percentage and OPS. He's carried a team filled with black holes like Delmon Young and Nick Punto to a division title, the absence of his running mate Justin Morneau making the feat all the more impressive. If he hadn't missed the first month of the season, we might be talking about one of the best performances in major league history. As is, Mauer's '09 ranks with Mike Piazza's greatest hits among the best campaigns ever put up by a catcher.

    Ben Zobrist was even better.

I don't believe that my friend Jonah really believes that Ben Zobrist was better than Joe Mauer. Zobrist did finish just very slightly ahead of Mauer in FanGraphs' Wins Above Replacement. But as Jonah notes, Zobrist gets an immense amount of credit for his defensive work, and particularly at second base. While there are good reasons to think that Zobrist is a fine second baseman, we just don't have enough data yet to confidently rate him as the best in the majors (by a lot!); I've got him third (behind Dustin Pedroia and Chase Utley).
And as Jonah also notes, aside from a generic adjustment for being a catcher, Mauer gets zero credit in WAR for his defensive contributions, the rationale being that we just can't measure a catcher's skills with any degree of accuracy or confidence. Well, OK. But he did win a Gold Glove last year, and I have rated him as the sixth-best catcher in the majors. There seems to be a pretty good chance that he's above average, and thus worth at least a few extra runs.

Mauer deserves to win, and he will. I think the real question isn't whether or not Zobrist deserves to win (he doesn't), but rather how many MVP voters will place him among the top five candidates. Because he probably does deserve that. These tests -- who's really paying attention, and who's not -- do seem to come every year, don't they?