Looking at the Rangers roster, you might be mistaken in thinking that they have plenty of depth on the blueline. The team now has ten blue-liners with NHL experience on the roster, and a further three who'll be under contract this year.
The starting six - barring injuries - looks pretty much set for the start of the season. Dan Girardi, Ryan McDonagh, Michael Del Zotto and John Moore are expected to be rejoined by Marc Staal and Anton Stralman, who both finished the season with injuries.
Behind them, new acquisitions/signings: Aaron Johnson, Justin Falk and Danny Syvret will be looked to in the event of an injury, as well as perhaps Stu Bickel. Rounding out the roster is Dylan McIlrath - continuing to work back from a major knee injury - and pro rookies Connor Allen and Tommy Hughes.
If you look at last season, the Rangers ended up using ten defenseman, including waiver pickup Roman Hamrlik and Moore acquired in a mid-season trade. The combination of Hamrlik, Matt Gilroy and Steve Eminger accounted for 68 games, or around one and a third defensemen on average each night.
The season before they played eleven defenseman, with injuries sidelining projected starters Mike Sauer and Staal for significant time during the season. Going back to the 2004-05 lockout season, the Rangers have used 9,10,10,10,12 and 11 defensemen respectively.
Typically the team picks up one or two during the season, so you have to figure 9 or 10 of the current Ranger defenders have a good shot at playing this year.
Johnson looks like he'll be the first option, and appears to be Eminger's heir apparent. Eminger played 35 games last year, and all but one of the 12 post season games, but was not brought back.
Another option would be Falk, though the gritty blueliner is probably more Stu Bickel than Eminger in terms of his style of play. Falk did play 36 of the Wild's 48 games last year, and a further 4 in the playoffs in his debut in the post season. There's some question as to whether Falk can improve his positioning, but the Rangers saw something they like and have been looking for an extra edge back there.
As for Syvret, he is probably no better than a third option at this stage of his career, and hasn't seen any NHL action since 2011. Finally Bickel has proven serviceable if given a limited role, and perhaps might even be ahead of Syvret in terms of a call up.
Of the three remaining defenders, Conor Allen is one that bears watching. The undrafted free agent signed on with the Rangers in the spring, and caught the eyes of more than one observer during the Rangers' Prospect Camp. This will be Allen's first pro season, so it remains to be seen whether he can make the jump.
McIlrath still looks like he might need some additional work in the minors, but a strong start to the season would see his stocks rise. At this stage it looks unlikely that he'll make the jump this year.
Finally, Hughes was another undrafted free agent signing, and will likely need at least a year in the minors before the team knows whether he has NHL potential.
Talk of a possible trade of Staal or Del Zotto seems very premature given the Rangers needs and depth. It is possible that they would consider a trade that brought in extra depth on defense, but that might be more likely after the season has started and injuries have been assessed, along with the capabilities of the new acquisitions.
Simply trading Staal or Del Zotto for other areas of need doesn't help the team, as much as it would likely hurt them.
In the end the retention of Brad Richards has reduced the team's ability to add depth, and as such they'll have a fine line to walk through this season.