TL;DR - I don't think either team bothers with chatting if they weren't backed into a corner. Because of how quiet the off season has been, annoyingly, this rumor could have legs.
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With McDonagh and Josi as LD, I don't fully understand why the Preds would want Hanifin. Too much quality LD vs lower quality RD. Unless their plan is to extend + train up Hanifin and then trade him for a haul Nashville dman factory style. With the quality of their RD, rolling 3 lines with Josi, McDonagh and Hanifin would be weird but not completely ridiculous. Plus with Hanifin's cap structure, they have options. But don't the Preds need forward help more than defensive help? They could make it work in taking Hanifin, but... why?
Flames, I could see the logic of them target a player like Fabbro. We're ultra thin on RD on the roster (Weegar actually prefers LD even though he's a RHS) and with Tanev often injury prone, RD is a bit weak/potentially dire. I'm not totally certain on the LD/RD aspect when Kylington returns, but certainly there's some juggling options on the second pairing no matter what with whatever might happen with Hanifin (wants to go to US)/Tanev(IR)/Kylington (up to speed)/trade* (fit?). I can't imagine a prospect of high enough calibre that Nashville would add to make the whole idea seem less weird. Flames are backed into a corner and they know it.
But then there's major weird aspects for both sides. Super stacking LD on the Preds seems weird if there are no additional moves to be made for their blue line. The Flames are taking on the biggest risk and likely doing a quality for quantity trade here (might be forced due to circumstances) where the value isn't great for them if they do it now.
Why wouldn't the Flames consider the TDL to trade Hanifin instead and shouldn't the preds be targeting some young forward with Fabbro vs another dman? Like, it's not bad enough that it doesn't automatically make sense to disregard for both teams, but it certainly smells more like a plan C than a plan A or plan B type of move.
Given the cap circumstances of most teams and how quiet the off season has been so far, this facet annoyingly seems like it's adding smoke and credibility to the basis of whether the two teams are actually conversing. Almost like two GMs blowing steam and chatting about how they'd rather benefit each other rather than some other asshole out there openly exploiting the fact they know these guys are backed into a corner.