I hated the Mantha trade when it happened but lets be real. He's a veteran 6'5 230+ lb winger still in his 20s. Even though Tom Wilson he is not he doesn't shy away from physical play. He was acquired as a RW whose bread and butter in the NHL was sniping from his off wing and was played as a LW without any defined role by our 200IQ organization. He's had good underlying this year until falling apart towards the end of the year playing for a lame duck coach that completely lost the team.
Given that he's only signed for 1 year @ 5.7 million and most UFAs of note will get massive term, there will absolutely be at least one GM that will be interested in him as rebound candidate in a contract year. My bet is on Carolina with their 30 million cap space next year and their willingness to take Pacioretty at his full cap last year and Puljujarvi at the deadline, and general strategy of getting maligned players and trying to turn them around. It's just a question of what the trade will be