The Royals have become one of the best teams in Major League Baseball thanks to a ridiculous bullpen and stellar defense.
Friday, that was the difference as the Cubs bullpen and defense imploded in the eighth inning, handing Kansas City an 8-4 victory in front of 34,273 fans in the Royals' first visit to Wrigley Field in more than 13 years.
"We played well today and then we broke down at the end," Cubs manager Joe Maddon said. "We had them on the ropes.
"They showed why they went to the World Series. We showed why we're not ready yet."
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Addison Russell tied the game for the Cubs with a long home run off Kansas City's elite setup man Kelvin Herrera — who had allowed just one homer in 80 innings since the start of the 2014 season — in the seventh inning, but the Royals wasted no time regaining the lead.
Pedro Strop walked Mike Moustakas to begin the eighth and the next hitter, Lorenzo Cain, doubled him home. Eric Hosmer then walked and after two straight strikeouts, the wheels came off for the Cubs.
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Royals second baseman Omar Infante sent a liner to center field, where Dexter Fowler dropped the ball and then slipped and fell while trying to pick it back up, allowing two unearned runs to score.
"We have to be more efficient in the latter part of the game," Maddon said. "We cannot make the physical or mental mistakes. You have to make pitches in order to beat good teams late.
"You have to have that will to beat them. You do that by repeating your fundamentals and your techniques and making your pitches or making players or having good at-bats and that's what we need to do, all throughout the game."
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The rough eighth inning overshadowed a comeback from the Cubs after Jake Arrieta allowed four runs — three coming on solo homers — in seven innings of work.
Kris Bryant doubled home Addison Russell in the third inning and Jorge Soler smashed a two-run homer to left in the sixth before Russell's game-tying blast an inning later.
"We didn't make the one play," Maddon said. "But it's before that. We didn't make pitches. The bullpen - we have to make pitches when it's necessary. We didn't do that and that put us in that particular bind.
"It was such a great game for 7 2/3 innings. I thought we really were gonna pull it out. Came from behind - Soler hitting that home run, Addy hitting the home run, working good at-bats in the game.
"And then you get to that moment and we just didn't execute. We talk about fundamentals and technique - we didn't execute and they win. It comes down to that."
The Royals tacked on another unearned run in the ninth off Edwin Jackson before Wade Davis and Greg Holland shut down the Cubs to preserve the win for Kansas City.
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"In moments like this, my thoughts always turn to - I want to see how high we bounce after the fall," Maddon said. "We've done pretty well this year, so let's see how high we bounce tomorrow."
On this homestand, the Cubs have welcomed the Washington Nationals and the Royals - two of the best teams in the league - into Wrigley Field.
The Cubs have hung with both teams, but are just 1-3 to show for it through the first four games.
"Those are both high-level clubs," Arrieta said. "The Royals played in the World Series last year and had some tremendous years from a lot of their young guys.
"It's good to match up with them. It kinda lets you know where you stand a little bit. Exposes your mistakes and where you need to get better at some things. We will.
"We were in that game right up until the end and we'll be better for it."