The "we don't need to score more" "we don't need a star centre" argument is ridiculous.
First of all, if we're going to play a centre on our roster 19 minutes, he had better produce more than 50 points.
Secondly, that argument begs the question "did you watch the games". Because if one did, the absolute black hole we have at the middle of the ice when another team's legit #1 skates out there is pretty obvious. It's not just about points, it's about keeping and controlling the puck which are major issues for the Leafs. Not to mention having a player with skills more appropriate for a linemate like Phil Kessel.
The Leafs need a major upgrade at centre, and it's not one a player like Joe Colborne is going to be able to provide from what I've seen.
I like Joe as a prospect and he is perhaps on the cusp of starting his NHL career. I agree that whether or not we think he "might" be able to do something in a couple of years, he is not on the top 6 depth chart going into next season, and cannot realistically figure in their plans - unless they were to throw Grabo onto the Kessel line and then attempt to work Joe C in over the next near with a best case scenario being Joe is a starter in 14-15. The buyout rules extend to next summer but I don't see that as relevant to Grabovski. Worst case is they retain some salary to move him for an asset, and this is not a temporary component of the CBA, so they could do it next season or any season after. So in two years the buyout costs of Tucker and Colby are gone and they apply the $2 million internal debt against Grabo's salary. He looks a lot more marketable locked in at $3.5 till 2017 and if he has 50+ points next season they should have a lineup of interested, cap stressed trading partners.
The above requires a lot of belief in Colborne the offense player though, and I can't see that he has shown enough for them to place any reliance on him. When he does suck, he sucks long and hard. And Joe is the jewel of their center ice prospects. If they don't want another small center, who is less physical and less of a playmaker than the one they just developed, then Grabo can't be in their long term plans either, so the salary retaining may work as well this year to deal him, as it would in the future. Of course if he has 60 points beside Kessel you would have more interested parties, or alternatively have to subsidize the trade less. But if he should not thrive beside Kessel (I don't expect this but one has to accept the possibility) then there is at least some chance his value is worse at the end of 13-14. For this reason, it isn't automatic that they would keep him another year.
I don't think most GMs have written MG off for one bad season, as even hall of famers occasionally have an off year, so he is certainly tradeable for positive value now, esp if salary is retained, but they either have to be willing to commit to Bozak for a few years, or they have to have a reliable replacement in hand to do this. If they are committing to Boz, they can just shop Grabo for the best return possible, because there is little potential lineup benefit in keeping him rotting in the bottom 6 with the offensively challenged, and he won't recover any trade value playing beside McClement.
If they know Boz isn't it, and they let him go, Grabs is the insurance while they attempt to land a Ribeiro or whoever (sorry but Weiss still looks like a 50 point guy to me). If they can't upgrade over the summer, Grabo remains the stopgap until they can. The UFA centers for 2014 look impressive, but Sedin, Datsyuk,and Malkin aren't coming to Toronto, so they choose between Pavelski, Datsyuk, and Bergeron for guys with any talent, and I don't see Bergeron coming. Pavelski looks better than Weiss, and younger than Ribeiro, but because he and Stastny are both effectively surplus on their current teams, they may be traded and resigned elsewhere without ever reaching the market. If the Sharks don't intend to extend Joe, then Pavelski is resigned there (100% chance if no Jumbo) and Joe, who turns 35 after next season, is the FA option. A bleak outlook if they can't make a trade.