He's really not that underrated. He was a really good AVG guy with longevity, but his career BB% is only 7.7%, so his OBP suffered. He led the league...
Will Smith had a 4.38 ERA, a FIP over 5 and was the Braves best RP in the playoffs last year. He had a 0 ERA in 11 innings. Lots of things can happen...