The price of a shutdown defenseman

One positive thing the Canes have (or "had" I should say at this point) was the emergence of Bryan Allen and Tim Gleason as a shutdown defense pairing. When these two were paired together, they took over 60% of their draws in their own zone, were constantly matched up against the opposing team's top lines and had 50% of the team's scoring chances go in the Canes favor. That pairing has since been split up with Allen being regulated to third pairing minutes (for whatever reason) but the Canes are going to have a big decision coming up within the next year as both players contracts are expiring and they might be forced to keep one or the other. Both are having great seasons and could have solid trade value in a few months for a team looking for a shutdown defenseman but the idea of losing these two is very troubling when you consider how big of a role they play. That's when it hit me. Just how much is the going rate for a shutdown defenseman in this league? Even ...