Reports coming out of Twitter (by multiple reliable sources) indicate that defensemen Matt Hunwick and Greg Zanon have been placed on waivers. (This might be why #22 is available for Nate MacKinnon.)
Hunwick was acquired by the Avalanche in 2010 via a trade with the Boston Bruins which sent Colby Cohen the other direction. Although Hunwick never really got his stride here in Denver, it was certainly a successful trade by the Avs as Cohen still has yet to become a roster player in the NHL. Hunwick played 76 games in an Avs uni, putting up 3 goals and 9 assists. His biggest asset was his skating, and he was amazing to watch. I shall miss him.
Zanon was a free agent signing in 2012. Although he was said to be a reliable, low-level pairing, he proved to be slow and ineffective with the Avalanche. His most prolific abilities with the team were blocking shots and rocking the bad ass beard. Zanon played 44 games with Colorado and posted only 6 assists.
The departure of Hunwick and Zanon clears up space for a possible free agent signing or a rookie making it out of camp. The most probable suspects are Stefan Elliott and Duncan Siemens. The Avalanche still have a full blueline, though, so battles will still ensue in training camp this fall.
There's a lot of disagreement about whether Hunwick or Zanon will be picked up off of the waiver wire or if they'll make it to Lake Erie. My guess (and I'm probably totally biased here) is that Hunwick will and Zanon might. Both are serviceable lower-pairing d-men and cheap against the cap. Time will tell.