You are acting like Vlasic has never been a top-4 D-man and he has no history in playing like one. Despite how bad he has looked generally this year, he has looked decent when he has played to his strength this year. It has been few and far between but he has definitely looked like a top-4 D-man. The problems with him mainly are:
1. Mental: Vlasic is trying to force the play too much in the offensive zone. Pinching when he should not be and leading to odd-man rushes the other way. Not sure if this is related to EK65 or something else, but its definitely mental. The games he has looked good this year, he has focused on the basics and played solid shutdown D.
2. Deployment and Pairing: Vlasic is being forced to eat hard shutdown minutes against other teams top-lines. This plus being paired with Braun who is also not having the best of seasons is most definitely not helping the case.
I am really hoping that the recent injuries to Vlasic and Braun are a blessing in disguise. It shows that the team can play really good D without either of those two and that we have options. PDB now has options on how to use and deploy them. Whether he chooses to do that or not, is a totally different issue.
Perhaps I miss-worded that. It would be more clear to say "I won't be considering Vlasic a top-4 defensemen
again...". I absolutely think he was top-4 in the past. In fact there were a few years I believe he was top-5 in the league and should have gotten Norris consideration, if the Norris wasn't all about offense anyways. So I think he has the skill and physical ability to still be a top-4 easily, but will he change his game back to what got him onto team Canada? We can only hope.
He has played that shutdown role vs top lines amazingly well in the past. I remember a stat from a few years ago about how he gets hard matched against Crosby, and Crosby had really bad stats because of it. I think there was even a quote from him about how he has always struggled vs Vlasic ever since juniors.
I think you are right that it is a blessing in disguise. Hopefully he gets slightly softer minutes, and sees that if he simply plays more of a defensive game he can really be a key to the D. If he can take 20-22 minutes a night with a little harder matchups than EK65/Burns, and focus on his defense, he will be invaluable.