A lot of Leaf fans know that Dion Phaneuf isn't good enough to play for the team for now and the future and here's why. First off he is overpaid. He was given #1 Defenseman money (7 year, $49 million) by former GM Dave Nonis and hasn't lived up to it. Secondly, he is not a leader and he has proved that on numerous occassions. He could not lead the Leafs to a playoff victory over the Bruins in 2013 and he couldn't lead them back into the playoffs the last two seasons. Most of us know that Dion Phaneuf isn't responsible for everything that happened but he has a huge role and isn't doing his part.
Also, he has started to decline. Three seasons ago, he was a #2 Defenceman on any contending team but he's only played like a #3 Defenceman the last two seasons which has made most leaf fans and the current management upset. At 30 years old, this isn't surprising at all but this is another reason why a trade must happen soon. He also takes a lot of heat from Leafs fans like I mentioned earlier which is why a change of scenery makes sense.