The Bruins said on Monday they have signed Sweeney to a multiyear extension, six weeks after they lost in the first round of the playoffs and three weeks after he fired Cassidy.
"Under his management, the Boston Bruins have been one of the winningest franchises in the league and a perennial playoff contender year in and year out," CEO Charlie Jacobs said. "While we recognize there is work to be done to achieve the ultimate goal of bringing the Stanley Cup back to Boston, I'm confident that Don's commitment to being best-in-class on and off the ice will help us climb that mountain once again."
Under Sweeney, the Bruins reached the Stanley Cup Final in 2019, had the best record in the league the next year and tallied at least 100 points in four of the past five seasons.
Of course, the same could be said of Cassidy, who was fired on June 6. The 2020 Jack Adams Award winner has since taken over the Vegas Golden Knights; the Bruins remain without a coach.
The Bruins noted in a release that the team is one of just four in the Eastern Conference to reach the playoffs in each of the past six seasons.
But team president Cam Neely credited that to Sweeney, not Cassidy.
"I've seen firsthand his tireless work ethic when it comes to all facets of front office management," Neely said. "He remains committed to doing whatever it takes to give the Boston Bruins the best chance to win every season."
That said, Boston has lost in either the first or the second round each of the last three seasons and is in an Atlantic Division where they have to face the likes of the Florida Panthers, the Presidents' Trophy winners this season, and the Tampa Bay Lightning, the three-time defending Eastern Conference champions.
Sweeney, 55, is fourth on the Bruins' all-time list for games played and ranks in the top 10 of the franchise's' career lists for assists and points by a defenseman. He joined the team's front office in 2006 as director of player development and moved up the ranks before being promoted to general manager in 2015.
The Associated Press contributed to this report.