The eleven rookies from playoff teams post-lockout are: Heiskanen, Brodin, McAvoy, Bear, Larsson, Zaitsev, Fowler, Carlo, Quinn Hughes, Fabbro & Myers. Zaitsev being on the low-end debuting at age 25. Bear was rushed into a prominent role in EDM and may bounce around. The rest are fairly reliably consistent top 4 D with about half solid top pair (Heiskanen, Brodin, McAvoy, Fowler & Hughes IMO). Aside from Hughes the rest were primarily mature defensively off the bat capable of eating minutes and earning trust. Fabbro is putting it together and may be the best comparable, albeit with only a few seasons of results.
While most of these guys are indeed consistent top 4 D, they all showed better than Fehervary in their initial seasons. These 11 players have played a combined 74 seasons with 500 minutes TOI or more. Of those 74, only 11 of those player-seasons were worse than Fehervary's past season. Of those 11 player-seasons, 5 of them belong to Tyler Myers, 3 of them belong to Nikita Zaitsev. And then 1 each belong to Larsson, Brodin, and Fowler, which appear to be outlier seasons based on their performance in other years. None were their rookie years.
Basically, there's no comparison for Fehervary to anyone aside from maybe Zaitsev or Myers. Neither are top 4 defensemen in this league. The rest of those guys have performed far and away better than Fehervary.
So again, it boils down to having to rely on this season being an outlier for Fehervary in order to make a compelling argument that Fehervary is going to approach the levels of the non-Myers/Zaitsev players in your list.
Of those I'd say stylistically Fehervary resembles Lindell, Dillon or de Haan. I don't view him as a one-dimensional offensive D. His deployment was not like Schmidt or Djoos. Of this group according to relative SAT% as a rookie Lindell fits best. Is he usually deemed a poor defensive player? His possession stats are historically poor but he seems like one of the league's better more traditional defensive-defensemen.
WAR shows Lindell as a very good defensive player:
He has had some poor possession stats that don't jive with your suspicion of him being a good defensive player, but that is exactly why a WAR calculation is so valuable. It contextualizes his teammates and competition. And especially on a one-line team like Dallas, the teammates he plays with is going to severely impact his performance on traditional possession metrics. Based on these and other factors, it appears your suspicion of him being a good defensive player is in line with the WAR data.
Is a player like Erik Gustafsson judged to be strong defensively primarily based on his possession stats?
No, he has been quite bad:
Likely because of the same contextual reasons mentioned above, WAR doesn't like Gustavsson defensively despite decent possession numbers and decent relative possession numbers.
Is a better Sekera type 3/4 really optimistic? I'm not saying he's firmly in the same category of a bunch of legit top pair defenders. We'll see about that. He's got some real hurdles to clear to consistently execute at that level. That projection was my sense prior to last season based on his profile and approach at various levels. I do think there are much bigger looming danger signs when it comes to overall team make-up. The weakness of the top six's possession game in general was a big issue, has been for a number of years when it matters most. It's often just Mantha playing around and then whatever anyone else can be bothered to do on a given shift. For a veteran group it's too inconsistent and soft...nowhere close to disciplined enough from a leadership/consistency standpoint. They also didn't have a coherent, effective third line to offset any declines. It was left to the checking line again to be the pulse. It's backwards and unsustainable. The defensive reliability of the team's centers and overall industriousness of the forward group is the #1 issue going forward IMO. It is not close to adequate and I have to wonder how long they'll be able to get away with it without significant changes. If the threshold now is that they need a new possession behemoth on the back-end to dominate and mitigate the forward mix then, sure, Fehervary is likely not the answer. But at the very least his cheap contribution of speed, versatility and edge remains sorely needed in the short-term. There are some underlying warning signs, sure, but the potential pending drop-off from other far more expensive and crucial core players strikes me as far more concerning.
Yes, I think it's quite an optimistic outcome at this point. Fehervary put up some pretty bad numbers this year. Andrej Sekera has played 16 seasons in the NHL, and of those he's only put up a worse WAR/60 than Fehervary's 21-22 season twice: in 2012-13 and 2017-18. Those were probably outlier seasons given his career WAR/60 numbers, shown below:
For reference, Fehervary's WAR/60 last year was -0.016.
It could happen, but it would have to rely on this being an outlier season for Fehervary and not his career norm. I'm just not confident that's the case even despite him getting COVID. It just seems like wishful thinking to me that he's going to massively improve next year when substantial improvement simply isn't very common for young defensemen.
Connecting this to my overall point when beginning this discussion, Fehervary is in some unique company when it comes to rookie deployment. He's in the same company as Heiskanen, Larsson, Brodin, McAvoy, Fowler, etc. when it comes to his initial use. Doesn't that at least seem to suggest that Fehervary would have some legitimate, perhaps substantial trade value? Those guys are good to great players.
And on the other hand, if in terms of overall impact Fehervary is closer to Tyler Myers or Nikita Zaitsev what's the real harm in losing him, especially if including him in a legitimate trade could help to plug another substantial hole in the roster? There are always TvRs available for cheap in free agency that could provide the same (or better) impact that Fehervary would provide if he truly was on the same level as a Myers or Zaitsev.