KANSAS CITY -- Now that was a home finale to remember.

In their final game at Kauffman Stadium this year, the Royals found themselves down nine runs in the fifth inning to the Mariners on Sunday afternoon. Then they found themselves leading by two runs after the sixth inning.

By the end, the Royals had hung on for a wild 13-12 victory to win the series and send the postseason-hopeful Mariners home in disbelief. The nine-run comeback matched the Royals’ largest comeback win in club history, previously done on June 15, 1979, in Milwaukee.

“Wow,” manager Mike Matheny said. “How about that for a finale at Kauffman? I’m still unpacking the whole thing of what just happened there.”

There is quite a bit to unpack. The bottom line is this: In a span of nearly 30 minutes, the Royals flipped a nine-run deficit to a two-run lead by scoring 11 runs against the Mariners in the bottom of the sixth inning. It was the sixth time in franchise history that the Royals scored 11 or more runs in an inning and the first since Sept. 9, 2004, at Detroit.

The Royals scored more runs in one inning Sunday than in all but four full games this season.

“That was one of the more wild games I’ve been a part of,” outfielder Ryan O'Hearn said. “It’s special. You don’t see it very often. Today was a fun one. It’s one I’ll remember for a long time.

“And to do it on the last day at home this season, in front of our fans -- it’s pretty special.”

An inning before, it was the Mariners’ offense making the noise. In a year full of struggles, the Royals’ pitching staff had one of their worst innings of the season when three pitchers allowed eight runs on four hits -- with four walks and two hit batsmen.

Max Castillo, making a spot start Sunday, struggled with command for four innings but had only allowed a run entering the fifth. That changed quickly when he faced four batters without recording an out, allowing two walks and hitting Ty France. Amir Garrett entered and needed 22 pitches for two outs while also hitting a batter and walking another.

“I think Castillo hit the wall right then, and then it turned into one of those innings you’d like to forget,” Matheny said. “But it made part of the story sweet, the fact that the guys kept fighting. I don’t know if I’ve ever seen anything like that.”

The Mariners’ win probability was at 100%. Kansas City has had a particularly rough time this season coming back from deficits; it wasn’t until this past Tuesday against the Twins that the Royals overcame a deficit of three-plus runs for the first time this season.

“When the other team has a long inning like that, you’re just kind of dead a little bit,” Hunter Dozier said. “You try to find a way to have good at-bats.”

Against Mariners ace Luis Castillo in the sixth, Edward Olivares walked before Michael Massey’s two-run homer cut the deficit to 11-4. Even after Castillo issued a walk to O’Hearn that knocked the right-hander out of the game, there wasn’t panic in the Mariners dugout at that point.

The Royals, though, could feel something.

“I don’t think a ton needs to be said,” Massey said. “It’s in us, in our blood. We’re competitive guys. Nobody likes to go out there and get beat by 10 or 11 runs.”

Walks and hits kept coming off a dominant Mariners bullpen. Matt Brash hadn’t allowed a run in his last 16 appearances dating back to Aug. 14. The Royals scored four off him Sunday without recording an out, including Bobby Witt Jr.’s two-run double.

Erick Swanson has been one of the Mariners’ steadiest arms all season, and the Royals pegged him for two runs.

The final blow came from O’Hearn for the go-ahead two-run double. Dozier’s single moments later ended up being the winning run for the Royals.

“I haven’t had a whole lot of moments like that this year,” O’Hearn said. ”It’s one I’ll remember and take with me, build confidence off of. I like being up in those situations. Always have been. I feel like I can get the job done. It was fun, that’s the only way I can describe it.”

The comeback marked the first time a team won after trailing by nine runs since July 5, 2018, when the Nationals came back and beat the Marlins. Between that game and Kansas City's win on Sunday, Major League teams had lost 820 consecutive games when trailing by at least nine runs.

The Royals bullpen held on in the back-end of the game, including Scott Barlow’s 24th save of the year in a game that many didn’t think he’d be pitching in. It ended a 5-1 homestand for the Royals as they head on their final road trip of the season, a nine-game swing through Detroit and Cleveland.

“Crazy inning, crazy game,” Dozier said.