There are a host of other relievers who would capably fill out a top ten list, but ultimately they fell victim to teammates ahead of them (Trevor May to Chapman on the Runners / Oliver Drake to Josh Hader on the Bums), and others just didn't have the overall level of dominance the four finalists did (Garrett Richards, Jeremy Jeffress, Shane Greene). So with all due respect to those Honorable Mentions, the four finalists below kept rising to or near the top.
In alphabetical order:
Aroldis Chapman - Rum Runners......................0 Saves.......0% SV%....3-1 record....1.78 ERA....0.91 WHIP.....147 BAA.....508 OPS....14.7 K/9
Josh Hader - Bako Bums......................................34 Saves.....95% SV%....2-0 record....1.20 ERA....0.91 WHIP.....139 BAA.....493 OPS....16.7 K/9
Hector Neris - Lakeview Rougarou.................32 Saves....94% SV%....5-8 record....2.83 ERA....0.93 WHIP.....178 BAA.....605 OPS....13.6 K/9
Kirby Yates - Pittsburgh Honey Badgers......30 Saves....86% SV%....2-4 record....2.77 ERA....0.94 WHIP.....177 BAA.....562 OPS....14.0 K/9