The Cubs needed to DFA Casey Coleman because it takes two days for a player to clear waivers, and he probably wasn't placed on waivers until today.
Also, Coleman will NOT have the right to elect free-agency if he is outrighted... If he gets outrighted, he must accept the assignment.
And he will not be eligible to be a Rule 55 minor league free-agent (6YFA) until after the 2014 season, so the cubs would retain control over him for another couple of seasons.
Additionally, if Coleman does get outrighted, he will be eligible for selection in the Rule 5 Draft, although he almost certainly won't get selected, because why would an MLB club draft him for $50,000 with 2013 roster restrictions when they could have just claimed him off waivers for $20,000 with no 2013 roster restrictions?
Just to review (In case the Cubs need additional 40-man roster slots later in the off-season):..
1. Alfonso Soriano, Carlos Marmol, Scott Baker, Shawn Camp, Scott Feldman, and Dioner Navarro have "no trade" rights (Navarro, Feldman, Baker, and Camp automatic NTC through 6/15 because they were post-2012 Article XX-B FA);
2. Matt Garza CAN be traded without restriction;
3. James Russell, Jeff Samardzija, Ian Stewart, Luis Valbuena, and Michael Bowden have the right to be an Article XX-D minor league free-agent if outrighted;
4. Alberto Cabrera, Welington Castillo, Jaye Chapman, Rafael Dolis, and Travis Wood are Rule 55 players, so they CAN'T be outrighted to the minors until the player signs a 2013 contract (player can be non-tendered, released, or traded, however); Once the player signs a 2013 contract, the player CAN be outrighted without restriction, and the player would NOT be eligible to a minor league FA if outrighted;
5. Chris Rusin, Trey McNutt, Christian Villanueva, Logan Watkins, and Rob Whitenack have Draft Excluded status, so these players CAN'T be outrighted or optioned to the minors until 20 days prior to 2013 MLB Opening Day. (they can be non-tendered, traded, or released, however);
6. Casey Coleman (who was Designated for Assignment today), Jeff Beliveau, Lendy Castillo, Geardo Concepcion, Zach Putnam, Brooks Raley, Arodys Vizcaino, Steve Clevenger, Darwin Barney, Starlin Castro, Junior Lake, Anthony Rizzo, Josh Vitters, Tony Campana, Brett Jackson, Dave Sappelt, Jorge Soler, and Matt Szczur CAN be outrighted without restriction and CAN'T elect free-agency if outrighted (presuming the player is not claimed off waivers).