I think he’s just being overused trying to play with Letang and Karlsson… I think he can be fine but I think they need a true number 5 defenseman who can rotate in with Graves and Pettersson to try to play the minutes that Letang and Karlsson are doing.
I'm not sure it's strictly "overused" in the sense of, too many minutes for him to handle. It's really not far off what he handled well in Jersey at all. I think it's more a case of...exactly
what sort of minutes he's being asked to handle. It's all wrapped up in the whole Karlsson thing...where they're so intent on keeping that guy away from tough matchups, and really only want to use their Top-4D overall...that he ends up shoehorned into a more true "shutdown" role. Which isn't his gig, and never has been.
It's the same as the issue with the "why is the powerplay so bad with all this talent???" The answer is...trying to shoehorn Karlsson in there. He becomes a focal point of the entire team, for better or worse. That has all sorts of spinoff collateral consequences like this.
Also very much a question of how suitable Graves is with a player like Letang, or especially Karlsson. He's never been a true "stay at home" defenceman. You really want him with a more conservative, passive puck-mover like Marino. Because despite being in a huge frame, Graves
is a rangy aggressive defenceman. Not necessarily aggressive physically all the time, but consistently aggressive in applying pressure defensively. He's an attacking defenceman. One of those guys who loves to play moving forward.
But that's pretty much the exact same as where Letang is at his best, so it's an awkward fit that forces Letang to play more conservatively. And Karlsson is an even more extreme example who basically defends by playing offense.