Ned Yost has taken a lot of flak for his decisions this year, ranging from his decision to use Yordano Ventura as a reliever in the Wild Card game, an unchanging line-up that has Alex Gordon hitting 6th, and the team’s reputation for aggressive sacrifice bunt attempts. But more than anything else, he came under fire for his strict adherence to bullpen labels, deeming them too important to deviate from, even when the season hung in the balance.

During the ALCS, though, Yost moved away from the rigid bullpen patters he’d been an ardent supporter of previously. In both games one and four, Kelvin Herrera was brought in during the sixth inning, recording six outs in the first game and five more in the finale. Wade Davis also was used to get six outs in the opening game, and then in the second game, Herrera and Davis were called on to pitch the seventh and eighth innings of a tie game. Instead of holding Herrera for the seventh inning only, or only using his big three to protect leads, Yost deployed them in a more aggressive manner, and the result was four more victories and a trip to the World Series.

While the defense was spectacular and Lorenzo Cain seemingly never made an out, the Royals bullpen was the MVP of this series, and Yost’s aggressive usage of his dominant relief corps is one of the main reasons why Kansas City looks unbeatable right now. Bullpens matter a lot more in October than in the regular season, and when they’re used as they were in the ALCS, they can turn a good pitching staff into an unhittable one.

In the piece linked above, I noted that elite relievers are asked to throw about 5% of a team’s innings in the regular season, but can push closer to 10% in the postseason. Here are the percentages of total innings pitched for the Royals big three in the ALCS:

Kelvin Herrera: 15.3%

Wade Davis: 13.5%

Greg Holland: 11%

Overall, the Royals bullpen pitched 43% of the innings in the ALCS, and Herrera, Davis, and Holland combined for 92% of that chunk. If you extrapolate those percentages to a 162 game regular season, Herrera would have been on pace to throw 223 innings, while Davis threw 197 and Holland threw 160. Their combined ERA in this series: 0.63.

In the ALCS, the Royals big three relievers had the workload of a starting pitcher combined with the leverage of a relief ace, and they were as close to perfect as you can get, with Holland surrendering the only run they allowed when the team had a three run lead. As Mike wrote this morning, the Orioles seemingly had no chance against the Royals bullpen, who just dominated the series in a way we rarely see.

The divisional round was characterized by bullpen implosions, with both the Tigers and Dodgers watching their relief corps implode in October. The Royals are here, in large part, because the A’s bullpen couldn’t hold a four run lead with six outs to go. Spectacular defense has been perhaps the most obvious sign of Kansas City baseball this postseason, but utterly dominant relief work is the biggest factor in why the Royals remain unbeaten in the playoffs.

Baseball in October is primarily different because teams can shift their innings allocations from the rotation to the bullpen, with the frequent off days allowing for concentrated usage among just the team’s very best arms. No team in baseball was setup to benefit more from moving innings from their rotation to their three best relievers, and so perhaps we shouldn’t be surprised that the postseason Royals are a better team than the regular season Royals. Their best asset has been magnified in the playoffs, and the results have spoken for themselves.

Of course, even the best planning and managing shouldn’t get you to expect a 0.63 ERA in the postseason. After all, I wrote about the theory of increased reliever value in the postseason to explain the valuation the Tigers put on Joakim Soria, and Soria was a dumpster fire for Detroit. Everyone wants a handful of dominant relievers who don’t give up runs in October, but building a unit to actually do that is a bit more difficult. The Royals couldn’t have expected this kind of postseason dominance, as even Herrera, Davis, and Holland weren’t this good in the regular season.

But when you have multiple shutdown relief aces, and a manager willing to give them 40% of the team’s innings total, you’re probably not going to be so easy to score runs against. Combine that with a great defense, and the Royals can seemingly hold any lead they get. While defensive value and bullpen performance are two of the more inconsistent traits in baseball, they can be hugely important, and the Royals are benefiting from elite performance from both areas.

The Royals aren’t winning with magic. They’re winning with three guys who throw 100 mph destroying their opponents, and doing so as early as the sixth inning now. Good luck to the Giants or Cardinals in the World Series; you probably will want to try and get a lead early.