I am just thinking through this idea.

Celtics want to contend for one last season and they need help.

Sullinger is a talented Rookie, but with injury issues.

We want to dump JJ.

It would be a risky move, but we are losing JJ anyway.

Sullinger would be a great bench scorer next year if he can come back healthy, if not he is only guaranteed through next season (3rd year for rookies is team option right?)

I haven't jumped on the trade machine to see if it works, but this seems like the kind of deal that benefits both teams in a way. Celtics could still value Sullinger as a future asset, but the injury really lowers his value, since that was a red flag around draft time.