By February of 2009, Riley was already focused on the Summer of 2010. He knew there weren’t any realistic free agent targets for the Heat with only the mid-level exception to play with. The Celtics were the defending champions and he wasn’t going to make his team a contender with just the MLE to play with.
So Riley dangled Marion’s expiring contract in front of Colangelo with the caveat that he take the remainder of Banks’ horrible deal. Toronto wouldn’t be able to get completely out from Jermaine O’Neal’s contract but they’d free up a lot of cap space, even with another season-and-a-half owed to Banks.
Here’s what I wrote a week prior to the trade when it became clear that the Raptors were intent on moving O’Neal:
“The problem with trading O’Neal is that the Raptors don’t want to trade him in a way that would do another team a favor by handing them a huge expiring contract that will give them the cap space to steal Bosh away from them.”
And that’s exactly what they did.
Had Riley not found a taker for Banks by the 2010 trade deadline then there’s no way he’d have been able to both re-sign Dwyane Wade and sign LeBron James and Bosh.