A trade never happened, and he actually signed a two-year, $8 million extension with the Bruins at the 2022 Trade Deadline. To add on, he rescinded his trade request not long after head coach Bruce Cassidy was fired.
DeBrusk stated after the game seven loss to the Carolina Hurricanes that he didn't know what the future held for him in Boston, however, general manager Don Sweeney confirmed in July that the 25-year-old indicated he'd like to stay with the team.
Whether DeBrusk rescinding his trade request and Cassidy leaving Boston are related remains up for debate and likely is something we won't ever know the truth about.
Cassidy recently joined Conor Ryan of the Boston Sports Journal to discuss the situation:
DeBrusk moved to the right side and was promoted to the Bruins' top line with Bergeron and Brad Marchand in February and saw a massive offensive jump for the remainder of the season.