This almost never works. Players typically view such trades as an affront and take them personally.
Yeah, that might be true in general when there are many years of service and a sense of belonging, but this is really not the case here. That's a probable reaction when Calgary traded him.
Monahan is probably no dummy. He understands where he was traded, the reasons he was traded, how he was traded (sacrificing a 1st to get rid of him) and the outlook that comes with it, which is that this team won't make the playoffs and since he's a pending UFA, there's a high likelyhood he will be traded. A negative reaction to this would be kinda childish.
It's as if players who are constantly told by their agents how this is a business and they have to be paid their worth, yet on the other hand be completely blind to the reality of having a first attached to yourself in a trade that sends you to the league's worst team for your last contract year.
Also, it's as if Hughes can't sit down and talk to him and any outcome is an emotionally driven Bergevin catastrophy like the way he dealt with Radulov and Markov, or Gallagher at the other extreme.
There are ways to convey the inevitability of Monahan's situation without turning it into a negative event.