Dunn will remember the night of his 400th as a bittersweet occasion. He wanted the homer to come in conjunction with a White Sox win, but it wasn't to be.
The White Sox committed a season-high four errors, didn't do much against Kansas City starter Bruce Chen and couldn't prevent late tack-on runs after drawing close.
"This game was kind of a disaster from the get-go," Dunn said.
The Royals are now 7-4 against the White Sox and continue to do the Tigers some favors.
"To me, their record [53-66] doesn't indicate how good [the Royals] are," Dunn said. "They put the ball in play and put a lot of pressure on your defense. If you aren't making the plays in the field or making pitches, they are going to make you pay."
The tone was set in the third inning, when the White Sox committed three errors with a light rain falling. Second baseman Gordon Beckham was charged with an error when he couldn't handle a throw from left field as Alex Gordon tried to stretch a bloop hit into a double. Gordon was called out, then safe when umpire Bill Miller noticed that Beckham didn't hold the ball.
That play loomed large moments later, as Billy Butler singled home a run to make it 2-0. Then Alex Rios had a chance to cut down the slow-moving Butler at the plate on Mike Moustakas' single, but the ball rolled past the right fielder.
It was that kind of slip-and-slide night for the White Sox.
"Tough night," said starter Jake Peavy, who allowed five runs (three earned) over 5 1/3 innings. "The Royals are a scrappy bunch, and the ball just bounced their way tonight."
The White Sox trailed, 4-0, when Paul Konerko hit a two-run homer in the sixth. It was the second homer in two nights for Konerko since he'd missed 10 days because of a concussion. After Eric Hosmer homered off Peavy in the sixth to make it a three-run game, the White Sox appeared to be going quietly.
But then Youkilis and Dunn provided some milestone madness before the Royals put it in second and roared away.
Dunn and Konerko are now the only teammates in Major League history to hit a 400th career homer in the same season. Konerko accomplished the feat on April 25.
"It's hard to enjoy," said Dunn, who now has 35 homers on the season. "Obviously, I wish it had come in a win."
Thanks to Baltimore's win over Detroit, the White Sox (65-54) maintained their 1 1/2-game lead in the American League Central.
"We just gave them way too many chances," manager Robin Ventura said.
The White Sox will try to salvage one game in the series on Sunday, and a priority will be containing Butler, who is 4-for-7 with four RBIs through the first two games of the weekend set.
Peavy is now 0-6 with a 5.53 ERA in his last seven starts against the Royals.
"I don't know what it is, because he has great stuff," Kansas City's Gordon said. "Sometimes some teams just have your number, and it works both ways."