Except that if the cost to potentially get a top player is next to nothing then you do it regardless of need. Same principal for drafting the BPA instead of need. If Edmonton was drafting need they would have taken Fabbro (RHD), they didn't because that's stupid. You can fill a need via trade (which they did, bad deal or not).
Leafs take this and run. They then attempt to move Greening & Holland for a depth defender with a higher one year contract (if possible) freeing up more spots for Brown, Leivo, etc.
That's how you build a great team with excellent asset management. Worse case we are wrong and lost a 4th and Corrado. We moved a 4th for Marincin which could have been a bad move but it was worth the "risk".