I might be alone in this, but I think Bieksa can keep up just fine.
My issue with him is that he still tries to play like he's the same player he was when he was younger. I actually think he could be a pretty solid 3rd pairing defenseman, if he was willing to simplify his game, play more conservatively, and just stop playing like an ******* in a pick up game. That's my real beef with him. It was the same issue I had with Sbisa before he was shipped out. Bieksa plays like he thinks he's the best player on the ice, and he can get away with it. He never really plays with urgency, and even when he ****s up he kind of casually glides back to where he needs to go.
Bieksa was twice the player someone like DiPenta was, but I'd rather have DiPenta on the ice because at least he understood his limitations and tried to play to the role that he neede to. If Bieksa did that, I think we would have had a pretty solid 3rd pairing guy. An overpaid one, sure, but that's on Murray.
It's all kind of irrelevant, because Bieksa wasn't willing to play within his limitations. That's on him.