3) Brian Dumoulin
Out of all the players mentioned, Brian Dumoulin has had the most experience playing with Sullivan. He spent 10 seasons with the Penguins, eight of which were spent while Sullivan was behind the bench. Dumoulin was a key component of the two-cup runs, being one of the most dependable defensemen. In his 10 years in the steel city, he registered 19 goals and 120 assists for 139 points.
Dumoulin is one of the better defensive defenseman in the NHL. His 6'4" stature allows him to play an effective shutdown game that suffocates offenses. He is also not afraid to take long shifts, averaging 20:07 of ice time per game over his career. While not the most physical, he is able to hold his own and not get bullied on the ice.
This is the exact type of player the Rangers are in desperate need of. Defense has been a major area of need for the Blueshirts. The blue line has struggled and has needed an upgrade for years, and Dumoulin would be the perfect player to fix it. He can bring the defensive responsibility and physicality that have been missing.