The 35-year-old forward has three points (one goal, two assists) in 16 games with the Bruins this season. He last played Jan. 9, when he was held without a point in 8:35 of ice time in a 5-4 win against the Winnipeg Jets. His last point, an assist, came in a 4-3 overtime loss to the Chicago Blackhawks on Dec. 5. He has been a healthy scratch in 10 of Boston's past 13 games and missed 13 games in November with a concussion.
Backes cleared waivers Saturday and will be assigned to Providence following the NHL All-Star break.
"We're going to look at younger guys and just felt at the end of the day, you do what's best for your team, what makes you the best team," coach Bruce Cassidy said. "Ultimately [general manager Don Sweeney] put him on waivers, feeling that was the best thing.
"... I know David doesn't agree with the situation, but that's the decision we made for the good of the team. I respect David as a person, as a player. We just felt we had better options, and that's how we're going to go forward and see how it plays out."
Backes signed a five-year, $30 million contract (average annual value $6 million) with the Bruins on July 1, 2016, after playing his first 10 NHL seasons with the St. Louis Blues. He has 554 points (245 goals, 309 assists) in 944 NHL games, and 39 points (17 goals, 22 assists) in 82 Stanley Cup Playoff games.
Cassidy said figuring how to best utilize Backes was a challenge dating to last season, considering his play and how it lined up with the current NHL, as well as his past injuries. Backes has a history of concussions and sought a second opinion after sustaining a blow to the head in a collision with Scott Sabourin of the Ottawa Senators on Nov. 2.
"[He's] a guy that you know is a dad who has two young girls," Cassidy said. "You always want to be careful that you're pushing guys to play a certain way. But now you've got a guy that, who knows, might be one hit away from having some damage. You've got to be really careful with that. I know it's a business, but that is the human side of it. So that was a bit of an issue for me to try to push him in that direction. So you talk about a different direction, we just felt [a forward] like [Karson Kuhlman] or [Anton] Blidh has more pace to his game to go that route with David."
Forward Brad Marchand said he felt bad for Backes, calling him a great teammate and friend.
"This is the part of the business that really [stinks], when you get into numbers games and you get into situations like this," Marchand said. "You don't ever want to see a guy get treated in this kind of way, especially a guy that's put his time in and earned his stripes, and he's been such a great player in this League for a long time.
"I can't say enough good things about him. He is just such a great person, great friend, and he's going to be missed in this room. We relied on him a lot on and off the ice, and he carried a lot of weight with the guys. We're going to miss him there, no question. But we wish him all the best. He's been an incredible teammate. We love him here."
The Bruins (28-9-12), who lead the Atlantic Division, play at the Pittsburgh Penguins on Sunday (12:30 p.m. ET; NBC, TVAS).