The Rule 5 Draft is basically like an expansion draft in any other sport. It's purpose is to prevent teams from stockpiling major league ready talent in their minor league systems (thank you Wikipedia). Teams protect their biggest prospects, and the other teams then choose from the remaining players in their system. The one catch is that the player must remain on the major league roster, or they are returned to the team from which they were drafted. It's the unofficial end of Baseball's Winter Meetings.
The Nationals came out of this year's draft with arguably the most sought after prospect, according to Adam Kilgore of the Washington Post.
The Nationals selected right-handed pitcher Elvin Ramirez from the New York Mets' Class AA affiliate with their first pick in the Rule 5 draft, a possible coup for a right-handed reliever who can hit 98 miles per hour with his fastball ... some expected he would be taken first overall in the Rule 5 draft once the Mets chose not to protect him.
The Nationals also took Brian Broderick from the Phillies, another right-handed relief pitcher. Both players must be on the Nationals major league roster, or they will no longer be part of the organization.
Any time you can pick up a player with a 100-mph fastball for basically nothing, it is a good thing for the organization. If Ramirez pans out, he could add a real power arm to what proved to be a pretty effective bullpen last year.