I watched Papelbon when he was in Peoria, and he was very good there, but he was primarily in the starting role with the Chiefs. He went 9-6 with a 3.11 ERA with a 1.17 WHIP. He had 107 IP, only gave up 7 homers and 30 walks, with 99 strikeouts.
My concern about him is that he will be 26, and that is getting "up there" in pitching years.
Here is a really interesting article that Jeremy and his twin brother Josh (who also is in Minor League ball) did: http://www.oceanviewpress.com/id97.html