With the series on the line against an American League Central opponent, the Royals went into Sunday afternoon’s rubber game against the Twins knowing it could be close and they would need to take advantage of any mistakes.

In the 13-4 loss at Target Field, Minnesota ended up as the one taking advantage of the mistakes. Kansas City ended its nine-game, three-city road trip with a loss, but the club heads back to Kauffman Stadium with a winning 6-3 road trip and a hold on first place in the division.

“There were a couple momentum plays that we needed to make, could have potentially changed the way they were going,” Royals manager Mike Matheny said. “But that’s kind of the name of the game. You come in today and feel like this is going to be just one of those tough, close games we’re going to have to play really clean baseball and take advantage of mistakes.

“They took advantage of the mistakes.”

The first of those mistakes came in the third inning, when the Twins erupted for seven runs. Only two were earned. Brad Keller gave up a two-run home run to Andrelton Simmons with one out and then allowed a single to Luis Arraez.

The inning could have been over after the next batter, Josh Donaldson, hit a sharp grounder to third baseman Hunter Dozier for a potential double-play ball. But Dozier bobbled it for an error to put runners on first and second.

“Normally when I see a ball down, that means go get it,” Dozier said. “But with him, how hard he hits it, I should have just drop-stepped. It was a tough play. I tried to keep it in front, but when you’re playing third, if you make the wrong move from the get-go, it’s tough to recover.”

And then the inning continued to spiral.

Byron Buxton hit a soft grounder to third base, which Dozier fielded cleanly, but he made an errant throw to score another run. Dozier said he shouldn’t have thrown it at all considering Buxton’s speed, but he was trying to get the Royals out of the inning with limited damage done.

The Twins pushed another across on a sacrifice fly and a three-run homer from Mitch Garver capped the big inning. Keller is the first Royals pitcher to allow at least five unearned runs in a start since James Shields was charged with six on April 12, 2014, at Minnesota.

“Brad just had trouble finding his location, and then when he did make some pitches, we had a couple blips that ended up hurting him,” Matheny said. “We know the way he throws, we’re going to need to make plays behind him. So that snowballed. Made it worse than what it was.”

After facing the minimum number of batters through two innings, Keller got out of the inning with a strikeout, and he pushed through 4 1/3 innings total. The big inning wasn’t entirely Keller’s fault, but it was frustrating nonetheless for the Royals’ Opening Day starter searching for some consistency this season.

He now has an 8.06 ERA in six starts and has yet to string together consecutive solid outings.

“It’s really frustrating, because I feel like I’m trying to build off the last start and getting kicked in the teeth again,” Keller said. “It sucks. That’s the name of the game to go out there and give your team a chance to win every time you go out. Seems like, right now, it’s a rollercoaster ride. One’s good, one’s bad. You try to steady the ship and become way more consistent.”

The Royals’ offense did what it could to make up for the big inning. Dozier hit a three-run homer — a positive sign as he’s struggled with results early in the season — in the fourth, and Whit Merrifield’s RBI double in the fifth put the team within striking distance. But the Twins put up three more runs in the sixth against lefty Kris Bubic and right-hander Scott Barlow, and rookie Alex Kirilloff launched his fourth home run of the series — a three-run shot in the eighth — off Jake Newberry.

For the Royals to continue their strong start this season, they know they won’t be able to have games like Sunday pile up on them, especially with Cleveland and the White Sox coming to Kauffman Stadium during this week’s homestand.

“It was a very good road trip, did a lot of things well,” Matheny said. “Just this one and the first game here, too, both of those don’t feel very indicative of the kind of club we’ve been all season. You just got to let these go and get ready for a good homestand.”