Erik Karlsson has had not just a bad series, he has had a very bad year.

Think of Mark Stone vs. Erik Karlsson. Before the deadline Mark Stone was on the worst team in the NHL, yet he still had one of the highest +/- goals in the league. Even though his team was regularly getting beat, Mark Stone had a +14, which was top 3 in the league at the trade deadline (i'm just going from memory here because I'm a Knights fan). Mark Stone is 26 and signed a long term 8 year contract at 9.5M a year.

Now, Erik Karlsson's primary benefit is he is a scoring defenseman, beyond that, as I said in the OP, I think one year ago he was also the best player in the league. He was fast and could lock down a primary forward/centerman. But he is just not playing that way anymore and he has nagging/chronic injuries hobbling him now throughout most of this year. This would be extremely concerning for me as a GM. A player that is already showing a problem with getting back to form. Its like signing a Derrick Rose or a Grant Hill. Sure they had great talent, but the injuries should be SIGNIFICANT concerns. This postseason he as a +/- that is worse than his goalie. That is hard to do. Watching the games it is clear that many of the goals are coming because he is not getting around to defending his assignments, he is consistently a step or two behind.

The Connor McDavid argument is not a fair comparison at all because Connor McDavid killed it this year.