Royals star Salvador Perez went 0 for 2 with a walk and finished in a tie with Toronto's Vladimir Guerrero Jr. for the big league home run lead with 48. Perez wound up matching the team record for home runs set by Jorge Soler in 2019.
''It was a lot of hard work and I thank God for this season,'' Perez said. ''To end the season this way was good and I think we'll only get better.''
Perez topped the majors with 121 RBIs.
Buxton hit his 19th homer off the left field foul pole to extend the Twins lead to 7-3 in the fifth inning. He missed over 40% of the season due to an oblique strain.
The Twins got to rookie Jackson Kowar (0-6) by scoring five runs in the first inning, three on Polanco's homer. Polanco's 98 RBIs this season are the most in Minnesota history by a switch-hitter.
''They played until the very end and gave us exactly what we saw all year,'' Twins manager Rocco Baldelli said. ''They took over the game and a huge part of winning this game and the organization. It's great to see them finish strong.''
Twins starter Charlie Barnes went 2 2/3 innings and gave up two runs and seven hits. Nick Vincent (1-0) got the win after throwing two scoreless innings.
''We won the last game and I'm happy for that,'' said Luis Arraez, who had three hits and scored twice for Minnesota. ''I'm excited for next season. I think we have a good team, but we play hard and won a lot of games. We need to play baseball and that's it.''
Kansas City scored three times in the third, getting three infield hits in the inning, but trailed 5-3. Nicky Lopez hit a single in the inning and was then pulled from the game, becoming the first shortstop in Royals history to hit .300 in a season.
''I think we improved, but it's all lip service right now,'' Royals manager Mike Matheny said. ''Put your work gloves on and let's take the next step.''
The Twins ended the season at 73-89 and in last place in the AL Central after winning the division the previous two years. The Royals, who were 16-9 in early May, finished at 74-88.
The Twins and Royals open the 2022 spring training schedule on Feb. 26.
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