If the Leafs were going to trade for someone to play with Rielly, it would be a stay at home guy, to let Rielly get back to the 70 point dman he can be. He's not the liability that guys like Karlsson or Mike Green are/were, but when he's playing his offensive game, he's not the best defensively. Average at best. He cna play the role of defensive dman, reasonably well, and has done that for the Leafs in the past, but he's never brought both the high end offensive game, and high end defensive game, at the same time.
But I can't see Myers being the guy they target to play with Rielly, I just don't think he's good enough to actually be the dman that frees up Rielly to be a 70 point dman again. I think it's pretty clear they're playing him with Brodie. Perhaps a Rielly/Holl pairing might see some ice at times, if there are games they go with 2 balanced pairings (Rielly/Holl and Muzzin/Brodie, instead of Rielly/Brodie and Muzzin/Holl), but Muzzin and Holl meshed pretty well last year as a decent shutdown pairing. My guess is they want to see if Rielly Brodie can bring the offense and be responsible as well, first.
Regardless, there is no way in hell Myers is worth Nylander, not really even close.