The Bruins (51-26-5) qualified for the Stanley Cup Playoffs in each of Cassidy's six seasons. They lost to the Carolina Hurricanes in seven games in the Eastern Conference First Round this season.
Cassidy was 245-108-46, and 36-37 in the playoffs, including a trip to the Stanley Cup Final in 2019, when the Bruins lost to the St. Louis Blues in seven games.
"A very, very difficult decision yesterday," Boston general manager Don Sweeney said Tuesday. "I met with Bruce in the afternoon. Both professionally and personally, I want to thank he and his family, Julie and Cole and Shannon, for what they've done both on and off the ice for the Boston Bruins organization. A really tough day overall. But I had to make a decision that I felt [was] in the best interest of where our team is at now and moving forward.
"I just felt that the messaging and the voice that was going to be required, I felt that we needed a new direction."
Sweeney said that feedback from the players was factored into his decision to replace Cassidy.
"They're not driving the bus in terms of making my decisions," Sweeney said. "I honestly believe that they impact our hockey club more than any of us. They're invested and I think they want to know how invested the organization is. I don't want to take anything away from what they're trying to accomplish as a group. I honestly believe that it doesn't matter what they're necessarily saying individually. It's collectively as a group and how much they think they can accomplish. And they agreed with me, because I used the statement that we had left something on the table and they felt the same way.
"Young or old, I think there's a message delivery that I think a new voice will resonate with them."
Cassidy was named Bruins coach on Feb. 7, 2017 after eight seasons with Providence of the American Hockey League, including five as head coach. The 57-year-old is 292-155-53 with nine ties in 509 games in eight NHL seasons with the Bruins and Washington Capitals.
"I think [the players] think, like I do, that Bruce is a terrific coach," Sweeney said. "And I think he'll have a terrific amount of success, as he did here, in his next opportunity. And I think every player would agree with that. He's a terrific coach."
Cassidy is the fifth coach to be fired since the regular season ended, following Jeff Blashill by the Detroit Red Wings (April 30), Mike Yeo by the Philadelphia Flyers (May 3), Barry Trotz by the New York Islanders (May 9) and Peter DeBoer by the Vegas Golden Knights (May 16). The Islanders hired Lane Lambert as coach May 16. The Winnipeg Jets announced May 2 they would have a coaching search and Dave Lowry, who replaced Paul Maurice as coach Dec. 17, could be interviewed for the job. The Chicago Blackhawks are conducting a search that includes Derek King, who replaced Jeremy Colliton as coach Nov. 6.
Rick Bowness stepped down as coach of the Dallas Stars on May 20.
"I have the utmost confidence in Don to conduct a thorough search to identify the best candidate that is going to help our team reach its full potential," Bruins president Cam Neely said.
NHL.com staff writer Amalie Benjamin contributed to this report
