The collective sleep schedule of Kansas City will get a little more normal over the next several days. The Royals don't play baseball again until Tuesday, October 21st. The Royals get 5 days of rest. Given that info, I wanted to look at how rest might affect the team.
I'll cite some previous research from Beyond the Box Score. Steven Martano found that regarding clinching the division, there is a sweet spot of rest. Too much, bad. Too little, bad. Somewhere around maybe 4-6 days of resting some percentage of starters is best for success at the beginning of the postseason. Scott Lindholm found that being the better team and/or the home team was a larger factor of success than being the better rested team. It doesn't seem like being the better rested team or having lots of rest will guarantee a higher chance of success, but I'd like to make the case here that the Royals desperately need the days off.
When thinking about rest for the team, Salvador Perez immediately floats to the top of my mind. We all generally know why--Ned Yost plays him every game. I want to give you more context around that. I went to FanGraphs and looked at a leaderboard since the arbitrary year 2000 to determine how Perez's workload compared to other catchers. Out of the 214 catcher-seasons, Perez caught the 7th highest number of innings. He was surpassed only by perennial iron man and former Royal Jason Kendall 5 times and a young Russell Martin once. Looking more recently, only Matt Wieters last year comes close to Perez's workload this year.
I'd also like to note some alarming performance trends. We know that Perez has gotten worse at the plate this year, but looking at his 1st and 2nd half splits really drove home the point for me: 116 wRC+ in the 1st half, 61 wRC+ in the 2nd half. Perez has been swinging more and more as the season has gone on.
Either Perez is "pressing" at the plate, attempting to do too much, if that means anything to you, or he's injured, or he's just completely lost. Whatever the reason, he's caught so many innings (including all of them in the playoffs, right? Where is Erik Kratz these days?), has such a poor approach, and got hit in the head a few times that a step back should at least help him not get worse.
The next thing I think about when I think of rest is the bullpen. The workload has shifted from the starters to the relievers; Dave Cameron summed it up quite well in this article. At their current playoff paces, the HDH trio would each throw a starter's workload over a 162 game season. The bullpen is obviously a huge strength for this team, and there is absolutely no reason not to rely on them. The trio made appearances in every game of the ALCS, every game of the ALDS (with the exception of Herrera not pitching in Game 2), and the Wild Card game. Thankfully, the built in days off have helped keep those guys rested, and these days off will certainly make them available to throw another 3-4 innings per game during the World Series if needed.
Finally, and I don't think this has been talked about a lot, there is Lorenzo Cain. Cain appeared in 133 games and numbered 502 plate appearances, which were MLB career highs. There has been some attention given to how Cain has learned how to take care of himself appropriately to withstand the grueling season. Nick Kenney and his staff are continually lauded for their work. However, Cain has surpassed this number of plate appearances in a year several times, including 2006-2008, 2010, and 2011. I think it's telling that we think Cain had a great year for health while ranking 39th of 59 qualifying OF in innings. Regardless of Cain's newfound "durability" or Kenney's work, Cain has to be tired after running around the outfield like his hair was on fire and also becoming a father. Cain is 100% necessary to this team's success, and these days off should help keep his legs ready to run down more fly balls in the World Series. His legend grows every day.
In other, perhaps more minor, ways, the days off should help other guys too. Alex Gordon ran into a fence. Mike Moustakas fell over a different fence. Omar Infante has a sore shoulder, and I think that bone spur in his elbow cited near the beginning of the season still bothers him. Danny Duffy has basically been on the 15 day bear costume wearing diet (AKA the "disabled list") during the playoffs. Yordano Ventura's last start was more fumes than fire. I don't think these more minor-ish kinds of things are unique to the Royals, though. I do think that since Cain and the HDH trio are so integral to the team's success, the days off might be more necessary for those players than for Gordon or Moustakas or whoever. That's what might make these days off more important to the Royals than any other team.