Quoting: BurgerBoss
What should be changed? I don't know if Devils need Vatanen that much, but Killer is a decent 40-point winger and Stephens is a decent prospect.
Unfortunately, the trade is both insufficient in value and incongruent with the Devils' needs.
First, on value: Even if Killorn is equal in value to Vatanen (which I'd disagree with), the Devils would give up the best, most NHL-ready prospect in this trade. Quenneville is a year older than Stephens, but he has been far more productive at the AHL level. Neither player is a top prospect, but Quenneville is a better bet to eventually play on an NHL bottom 6 (he will likely play on the Devils' fourth line in 2019-20). Ben Thomas has not shown NHL potential. The 3rd-round pick is not enough to bridge this gap, especially given that New Jersey also eats $2M of Cap in this trade; the Devils may have Cap space to spare, but that they'll still demand a premium to help other teams with their Cap problems.
Second, on need: To answer your question, the Devils do need Vatanen that much. He may be the best Defenseman on a team that lacks top Defensemen, and his ability to play either side of the ice has been invaluable. Meanwhile, New Jersey will have enough decent Forwards to fill out their middle-6 (especially with Hughes or Kappo on the way). If the team does need a middle-6 Forward, they could probably find one in Free Agency (one that may be cheaper than Killorn).
That being said, the Rangers trade is a cool concept. I don't know that the Rangers would give up a prospect in the deal (even if it means that they get less value from the Lightning), but the idea that Tampa could pay them to eat Callahan's contract is a good one.