1. Andrew Miller
You probably remember Andrew Miller being pretty good. Andrew Miller was even better than you remember.
Armed with a devastating slider and a killer walk-out song (God's Gonna Cut You Down), Miller was the piece the Yankees never should've traded during their 2016 hybrid sell-off. Clint Frazier and Justus Sheffield? Eh. Cleveland getting a multi-inning relief mastermind for the '16 World Series run, as well as 2017 and 2018? They won that trade. Would've been really nice for the 2017 Yankees to have Miller!! We digress.
Miller was a buzzsaw in 2015 after the Yankees coerced him to come over from the Orioles and fill D-Rob's shoes. 33 hits. 20 walks. 61.2 innings. 100 strikeouts. The walk total wasn't as problematic as it likely seemed in your mind's eye (again, Rivera, used to perfection, etc.). His WHIP still stood at 0.859, helping to keep an aging and befuddled Yankees team in playoff position (it's a shame he couldn't help steal the Wild Card Game).
Surely, Miller didn't get even better in 2016 after his career year -- oh, wait, yeah! As a Yankee, he struck out 77 men in 45.1 innings, allowing just seven earned runs (somehow on five homers). With Cleveland, post-deadline? Another 46 Ks in 29 innings and the enduring story of the postseason, considering the experimental way in which he was used.
Rivera was generational. Miller was evolutionary. It's a shame only 1.5 of his seasons were spent in pinstripes.