Wade Davis was as good as it gets in 2014
Unlike Herrera and Holland, Davis didn't come up through the Royals' system, instead being acquired as part of the controversial (at the time) deal that brought James Shields to Kansas City. Widely seen as a throw-in for that trade, Davis eventually had an even bigger impact on Kansas City's success than Shields. At first, however, things didn't look promising.
Davis had started and relieved and for Tampa Bay, but the Royals were intent on starting him. Unfortunately, Davis was middling, at best, as a starter. He went 6-10 and was back in the bullpen by the end of his first Kansas City season.
Like Herrera, though, he found his groove in 2014.
Handling the eighth inning, Davis posted one of the greatest seasons ever by a relief pitcher — he went 9-2 with a 1.00 ERA in 72 innings, set a team record for most strikeouts by a reliever (109), walked only 23, and finished with a 0.847 WHIP. From June 25 to Sept. 16, he didn't give up an earned run; his Sept. 15 ERA was 0.69. And he didn't give up a home run all season. In the postseason, he was 2-0 with 12 strikeouts and only two walks in 12 appearances.
Davis was almost as good in 2015, although he finally allowed a homer. And when forced to take over closer duties following Holland's injury, he didn't bat an eye. His epic performance in Game 6 of the 2015 ALCS, pitching around an extended rain delay, clinched back-to-back World Series berths for Kansas City, and he recorded the last out of the 2015 World Series.
The Royals traded Davis to the Cubs after the 2016 season, and he had a good year on the North Side before moving to Colorado in 2018 and leading the National League in saves. He returned to Kansas City in 2021 for one last hurrah, but it wasn't the same.