You're fallaciously assuming that Nashville's dire situation has...well...any effect on the value of the player. The "seller" (in this instance it's the Preds) in a "sellers market" that is already setting up for the deadline many months out as scarce in RHD available...has the value determined by what the "buyers" are willing to pay.
It's highly unlikely that Fabbro is going to be worth less than a 3rd round pick at the deadline. So that disincentivizes the idea of moving him now for that. The upside is, he's worth more than a 3rd round pick. The only real risk to hedge against is injury. Which...if he's only sometimes playing, is even furthered lessened.
Liljegren is a similar defenceman, though younger with a more positive trajectory at least. And maybe that's what Fabbro is "worth". But if you're the Preds...what's the incentive to make that deal now? He's not expensive. He's an expiring contract (unlike Liljegren). As long as Fabbro is healthy, he'll be more valuable at the deadline.
He's 28 years old and he's scored points literally one time on a Yotes team that was basically just wasting time. He's not a "soft" player and he's not an "unskilled" player. But he's not enough of either to be worth...literally anything to anyone as an NHLer. There's a reason the Yetis are allegedly "trying to move him". If he was a guy you want to have as a player, he'd be a guy Utah wants to keep. But he's not.
That has no value to anyone beyond teams who are, similarly to the Yotes last year...basically just running out the clock on the season. Who can use a filler player who has a little bit of skill and can play some minutes and maybe score some goals in them at an unsustainable rate. But those sort of teams literally never pay anything to acquire guys. They have other teams pay them to take on contracts and filler, in exchange for depth players who have a defined "role" on playoff teams.
I mean...i don't think we fundamentally disagree that much about Fabbro as a player. It's just...a "3rd or 4th" right now is basically nothing. There's at least an outside chance that he's worth more than that at the deadline. Especially considering how bleak the market looks. It's absolutely shaping up to be that "sellers market" where teams get stupid.
I guess the idea that Carcone is worth...literally anything, is the bigger point of contention. I just don't see why any team would trade anything other than a "contract swap" or struggling prospect or "change of scenery" or whatever for him.
He's not a terrible player. He's just...not the sort of player that good teams tend to want. And bad teams don't tend to spend assets for filler players.
It's like...Klim Kostin is a kind of bad, frustrating player. He's not even necessarily any better than Carcone. But if they both cost the same minimum amount on the salary cap...Kostin is the guy a team would want.