If Yak helps the Sens win, where his offensive contributions outweigh his defensive growing pains by a satisfactory margin, let him play. He won't get overwhelmed physically, 6'4 207. Seems like a confident guy who won't let mistakes get him down as he learns.
If the Devils / Habs can have small offensive defensemen on their bottom pairing, Yak can surely play bottom pair too. They need sheltering, tough for guys like that to handle big players in front of the crease. Which is why Brannstrom only makes $900K. Of course, those 2 will contribute a lot to their teams' offenses, so it's worth it to live with their defensive weaknesses as they help the team win.
I'm saying if really good young offensive d-men Casey and Hutson contribute in the NHL, on the PP, even strength minutes sheltered so they're not playing vs. offensive stars, Yak can be handled the same way.
If he's deadly on the PP, and generates a lot of offense, he needs to stay.
If his defense is intolerably bad, he needs to go down after 9 games. How much do you tolerate?
It doesn't help that Kleven, Hamonic, and JBD are so-so, Yak is clearly better. The top 4 needs to play a lot, and not have any long-term injuries.