I think if you're making this argument, it means their defense as a whole has collectively underperformed.
In terms of the on ice performance, I'd absolutely disagree. He's taken so many bad penalties and left the team in bad spot after bad spot given their struggles on the PK.
But the really interesting part is how many give aways he's had, especially when you contrast it with the amount of takeaways. It's a negative 21 differential. worst on the defense. He gives the puck up like it's his job, which it's not, and he doesn't get anyone on the opposing team to turn it over, which is his job.
He's also grossly overpaid. Money that should have been used to fill the top 6 hole at wing. But I digress...