I don't think anyone is seriously trying to blame one guy for the Canes defensive issues to start the season. Let me amend that ... I don't think anyone serious is trying to blame one guy. Plenty of people are doing it, but they're not people who need to be taken seriously.
That said, that third pair is a mess and one of them knows how to actually play defense, so ... Tony is an easy target. It's hard to call what he's been doing in the D zone good, so pointing him out isn't exactly wrong. In actual fact though, there's a lot going on with that forward line the third pairing has been working with and the Canes defend in 5 man units, not 2. KK has struggled to keep position in his own end, and I don't think Necas has shown anything like his best effort in the D zone ... and his decision making on D in transition has been worrisome at best. That line has also turned the puck over in dangerous areas WAY too much. A lot of guys have a lot of work to do to dial this in. The good news? Most of them have been there/done that.