When the Boston Bruins fired Bruce Cassidy, it marked the end of a lingering drama within the dressing room between the head coach and at least one player, although conjecture has it that several players felt uncomfortable under Cassidy. Cassidy openly demands a lot from his players, and even the Bruins' brass felt that a new approach was needed.
It cannot be said that it was as black and white as 'Cassidy vs. DeBrusk,' but the fact that DeBrusk rescinded his trade request -- submitted some time at the start of 2021-22 -- shortly after Cassidy's dismissal suggests that was a huge reason behind his decision. However, Cassidy maintains that his relationship with all of his players remain positive, and today DeBrusk shared his reasons for pulling his request:
"At the end of the year I said I'd talk it over w/my family & think things over. The biggest thing for me, honestly, was the support I got from the guys in this room. It felt like there was a lot coming at me & the guys kept it tight."
DeBrusk did not name Cassidy as the reason why, but if you read between the lines it is clear that the two sides were not on great terms. It is the tactic of many of history's best coaches to create a 'me vs. them' environment as a method of bringing players together. Alluding to DeBrusk's comments saying his teammates' support influenced his decision, it is not outright apparent that Cassidy was the reason behind DeBrusk's dissatisfaction.
That said, the two sides clearly were not a great match, and Cassidy's dismissal accompanied by the timing of DeBrusk's rescission is hardly coincidence. Both of them are likely being coy on hit microphones to keep things cordial. But we all know what is really happening behind the scenes.