Butler delivered a two-run single in a three-run ninth, as Kansas City loaded the bases with none out against Tigers closer Jose Valverde. Butler drilled the first pitch he saw to center, cutting the deficit in half. Yuniesky Betancourt then hit a 390-foot flyout to center for the first out and Jackson made another nice running catch on a sinking liner from Moustakas that scored Eric Hosmer for the third run of the inning.
With two outs, Jason Bourgeois -- running for Butler -- stole second base and represented the potential tying run. But Jeff Francoeur struck out to end the game, as the Royals dropped to 1-6 against the Tigers this season.
"It was too big of a hole," said manager Ned Yost. "I really thought that hit by [Betancourt] had a chance to [be a home run], but there was too much air under it. He hit it in about the deepest part of the park and Jackson is a great outfielder."
The Royals fell behind early when Chen (7-8) gave up a two-run homer to Prince Fielder in the bottom of the first to tie the game at 2. Butler and Moustakas delivered RBIs in the top half to give the Royals an early 2-0 lead.
Chen struggled with his location early, but appeared poised to escape damage in the first with Jackson -- who stretched his hit streak to 14 with a leadoff single -- at second base. Chen delivered a 78 mph curve to Miguel Cabrera for a strike three call and a second out.
Considering Cabrera had a career .476 average with three homers in 21 at-bats against Chen coming in, it was a good sign for the Royals. But Fielder followed with a two-run blast on a 3-2 fastball to right-center to tie the score.
"I made good pitches to Cabrera, but I fell behind [Fielder] and then left a fastball a little up," Chen said. "I'm not a power pitcher, so I need to keep the ball down and give my defense a chance."
Chen's struggles were only part of the story. The Royals stranded five runners off six hits and a walk in the first two innings.
In the second, the Royals left the bases loaded when Butler hit a sharp grounder right to shortstop Jhonny Peralta. The Tigers then went ahead for good in the bottom of the inning, when Chen allowed four straight hits that scored runs for a 5-2 Detroit lead, including doubles from Ramon Santiago and Gerald Laird.
After that, Fister (2-6) allowed three runners combined to get on base on two hits and a walk in the third through sixth innings. His most effective work came in the sixth with three ground-ball outs while retiring the side in order.
"We just keep battling and playing hard," Yost said. "Escobar had a great game for us [getting on base five times], but that doesn't surprise me."
Chen allowed seven hits in the first two innings, but got through the third unscathed. However, the Tigers loaded the bases with none out to start the fourth on two hits and a walk. Chen struck out Quintin Berry, but Yost pulled his lefty for long reliever Nate Adcock with Cabrera striding to the plate. Detroit's All-Star third baseman hit a sacrifice fly to make it 6-2 and Chen's final line was 3 1/3 innings, nine hits, six earned runs, two walks and three strikeouts.
It was a stark contrast to Chen's first start against Detroit this year on April 17, when the veteran went seven innings and allowed three earned runs on six hits for a quality start. Chen, though, took the loss in a 3-1 Detroit win. Last season, Chen was highly-successful against American League Central rivals, going 8-3 with a 2.47 ERA.
"Bruce never got locked in tonight," Yost said. "He just wasn't sharp."
"I feel very bad, because I didn't give me team a chance," Chen said. "I was proud of my teammates, because they had a great comeback. We almost pulled it out."
Moustakas finished with three RBIs and two hits, including his 15th homer of the season, a fifth-inning solo shot that made it a 6-3 game. Along with Butler's 16 homers this season, it's the first time two Kansas City players combined for that many homers by the All-Star break since 2003, when Mike Sweeney had 16 and Carlos Beltran hit 15.
Betancourt's sacrifice fly in the top of the seventh cut the the Tigers' lead to 6-4, before Delmon Young gave Detroit some breathing room in the bottom of the seventh with a two-run homer to left-center off Adcock, his ninth of the year and third in three games. It turned out to be a pivotal blast.
Adcock went 4 1/3 innings after relieving Chen, allowing zero earned runs and three hits. Although he did allow Young's homer, Adcock's work gave Kansas City's bullpen a much-needed break after a long road trip.
"It seems like every time there's that one pitch I want back," Adcock said. "I just need to eliminate that one mistake. The defense played great behind me and it's good to know there's a lot of fight in this club."
Yost has been pleased with his staff's middle relief all season long.
"Nate hung that one curveball to Young, but beyond that he was fantastic," Yost said.
The Royals will try to salvage Sunday's series finale before the All-Star break with lefty Everett Teaford getting the ball.