The Rangers would most likely need to retain 50% of his salary so that contenders can afford his cap hit. But if they do that, they can probably land a late 1st round pick and a decent prospect for him. Here are some examples from last season:
Kevin Shattenkirk for 1st + Zachary Sanford [+ conditional 2nd but conditions were not met]
Martin Hanzal for 1st + 2nd