Purely for PP QB ability, Sean Durzi is young, looked good with the Kings, wouldn't cost an arm and a leg, and they have a glut of RD. I joked about Ghost, but purely for the PP he'd be a solid asset and would come dirt cheap. Arizona could retain salary too. At 5v5, he's not much less reliable than Rielly - in fact, their GAR and xGAR profiles are hilariously similar. Edmonton needs to clear cap space and would move Barrie cheaply - he's a PP asset. Erik Brannstrom is running out of chances in Ottawa, but he's shown some PP touch.
As I said, at 5v5, you don't replace him. You just spread the minutes across Sandin, Liljegren, Brodie, etc. The team loses some 5v5 rush offense (which the Leafs were already near the bottom of the league at anyway), but improve defensively from Rielly's removal.