Good read here on Dion and the captaincy:
http://www.thescore.com/nhl/news/791932
A very well written article.
The other thing one has to consider, is that with Kessel, you could at least make the case, that the team was better off without him.
If they're going to buy into a no-nonsense, aggressive north-south game, with an aggressive forecheck, that isn't a game that Phil Kessel can play, and as a result, isn't a game that his line can succeed at. If you can get a player who contributes 20+ goals and 30+ assists, but has a much stronger 2-way game, the benefits to that line's time spent away from the defensive zone may offset the loss of his offence. I'm not neccessarily saying you
win that arguement, but there are at least points to be made.
The same cannot be said about Phaneuf. Here's a guy who does basically everything for you, and does a lot of very important things substantially better than anyone else on the team. No, he can't quite move the puck like Jake Gardiner or Morgan Rielly, no, his shot wasn't as effective as Cody Franson's, but neither of these were weaknesses either. On the flip side, in terms of who you'd want out against the other team's top opposition, or defending a narrow lead, Phaneuf was and is far away the most qualified defenceman to do that job.
The Leafs are in a bit of a interesting spot when it comes to the distribution of their forwards and D, especially considering that generally, defencemen take longer to develop than forwards.
In the NHL, Up front, the lineup has 2 young high output/upside guys in JvR and Kadri, and then a lot guys who would be described as "fillers", and of course there are 12 forward positions to fill. In the system, there's a ton of potential & high end skill with Marner, Nylander, Brown, Kapanen & Bracco. On D, at the pro level, the Leafs already have a couple of young high output/upside guys in Rielly & Gardiner who've proven to be top 4 defencemen. In the system, notably less exciting, with a bunch of guys who's ultimate upside is likely that of a #4 defenceman. If you believe that Phaneuf ages well in a more structured system / defensive minded role (I think he will), then really, all you're left looking for is one more top 4 guy... the last thing I think the Leafs want to do, is end up like the Oilers where you've loaded up on high potential forwards, they start developing, but you just can't get the defencemen required to take your team to the next level.