Playoff Roster

The Mets promoted Anderson Hernandez (and demoted Dave Williams) in order to have Hernandez available for the playoffs.
The playoff roster explanations are confusing but players on the DL can be replaced on the roster by players still in the minors, but position players replace position players and pitchers can only replace pitchers.
The Mets likely won't need to replace Sanchez, Zambrano or Juan Padilla though.
But they might want to use Milledge for Floyd (if he's still hurt) or find someone instead of DiFelice to take Castro's place at catcher.