Sorry to quote you again, but I just wanted to say that Zaitsev has been bad defensively not only this season, but he was worse last season (but we can attribute that mostly to his ridiculous minutes).
The thing that kept him in my mind as a "top-4 defenseman" was how he was arguably the best offensive defenseman on the team last year (with a brutal transition game). Everything except his defense has gotten worse this season.
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I've seen a number of stats that suggest he's horrible defensively by the analytical community, dating back to last year but part of that is systemic and part of that is circumstantial IMO. That's why I don't think analytics is a great take on Zaitsev as I mentioned earlier.
1) The Leafs d-men give the blue-line up, they never stand the line- fact (systemic? possibly but they certainly don't trap at the neutral zone/blue-line like we routinely see other teams do)......in fact, they always give the entry cleanly at the blue-line most of the time (if the opposing player has any speed through the neutral zone at all).
2) His best skillset, as you say, is as a PMD, but he's often the last person back/support d-man in that Gardiner pairing which shouldn't be favourable for a lot of the metrics we've seen. Particularly when your measuring any type of metric that accounts for exiting out of his own end, entering the opposition's blue-line (which is genuinely rare for a guy like Zaits).
Overall, I don't think he's nearly as horrific as the metrics say, and he's not great. He's kind of in a transition year, and certainly a #4D right now with upside. I think a guy like Zaitsev (personally) is a cautionary tale for analytics, and I'm generally pro-analytics, certainly for most team-wide measurements. But a lot of the defensive metrics like allowing entry denials, etc at the blue-line are pure grey-area.
Digging deeper, it's clear Zaits anchoring the PK last year is sort of reminiscent of Rielly last year (taken off the PP, anchored the PK)....sort of that developmental, dog-house year. I wouldn't say he's a finished product yet so there's room for optimism.
