Probably Travis Hafner. Didn't even make the all-star game and has .321 BA, 27 HR and 76 RBI's. He's been huge for the Indians hitting a lot of grandslams...the lack of attention he gets is ridiculous.
He isn't under appreciated, but it pisses me off that they downplay the value of David Ortiz because he's a DH. I don't think he'll ever win an MVP, just because he doesn't play a position regularly. David Ortiz is one of the top 3 most valuable guys in baseball.
I do agree with your views on Hafner. I thought he'd be a give in to go to the all-star game.
Vernon Wells is very underrated because he plays for a Canadian team, he's putting very good numbers this season, and he's one of the best defensive players in the game. But I also think that Hafner is underrated as well.