That and he doesn't play special teams. Those are generally around the amount of minutes Carrick or Borgman get.
Babs testing him on the right side with Rielly was promising. If he's effective on the right there might be a chance he either gets Carrick's spot or they move Hainsey with Gardiner (hoping it has the same effect Hainsey had on Rielly) and see if Dermott can excel with Rielly.
The real issue is, without Zaitsev, we have only 3 defenders Babs has any faith in on the PK, which is Rielly, Polak and Hainsey. So, its unlikely Babcock plays 3 of Borgman, Carrick and Dermott in the same line-up at the expense of Polak.