Ryan Doumit threw wildly to second on a stolen base attempt, and the runner eventually scored.
Josh Willingham lost a fly ball in twilight, allowing two runs to score.
Darin Mastroianni tried to steal third -- with the Twins down four runs -- and was thrown out.
"Not a very good ballgame for us," Twins manager Ron Gardenhire said. "Some mistakes out there."
On this particular September night, this particular non-contender resembled a team that's counting down the days until the end of the season.
And Kansas City took advantage, rolling to a 9-1 victory while ripping eight extra-base hits around Target Field. Twins lefthander Scott Diamond (11-7) took the loss while Royals rookie lefthander Will Smith, (5-7) beat the Twins for the first time in three tries.
The Twins didn't pitch well, from Diamond not having his good control to Luis Perdomo hitting Lorenzo Cain in the helmet with a pitch in the eighth inning. Cain, by the way, stayed in the game and finished a homer run shy of the cycle.
Diamond gave up four runs over six innings on 10 hits and three walks with two strikeouts. He has a 6.64 ERA over his past four outings. After starting 6-1 at home, he's lost his past three decisions at Target Field.