Boston will retain 25% of Backes' salary as part of the agreement. His contract is valued at $6 million annually, and there's one more year left on the deal after this season.
The Ducks selected Kase in the seventh round of the 2014 draft. The 24-year-old has appeared in 198 NHL games, amassing 43 goals and 96 points. The winger notched seven goals and 16 assists in 49 contests with Anaheim this season.
Backes, 35, has struggled to find his way into Boston's lineup in 2019-20. He's appeared in 16 games while tallying one goal and two assists. He was demoted in January, but Backes hasn't played in an AHL game despite being healthy since then.
The Bruins selected Andersson in the second round of the 2018 draft. The 20-year-old defenseman has recorded two goals and 22 points in 41 QMJHL games this campaign.