De Vries was sent back to Triple-A following the game.
"It's really frustrating, but coming here, I basically knew that," De Vries said. "I knew I was the 26th guy and the 26th guy usually goes back down. So I kind of figured that would happen. Obviously I would've loved to stay up here longer. But I knew the situation at hand. Nothing really surprised me."
The Eden Prairie native allowed one run on five hits and struck out a personal-best six on the way to his second career win. The six innings were also a career-high after he lasted five in each of his first three starts. Kansas City's lone run against him came on a Billy Butler homer in the second inning.
"I think he came up and did exactly what we were hoping he would do," Twins manager Ron Gardenhire said. "He got us deep into the game and pitched really well."
Trevor Plouffe took the Twins' home run lead earlier in the day with his 16th home run of the season in Game 1. But Josh Willingham resumed a tie with Plouffe when he hit a two-run shot off Royals starter Luke Hochevar in the first inning of the nightcap.
Chris Parmelee and Joe Mauer also hit solo home runs in the second and third innings, respectively.
Parmelee's -- off an 0-2 pitch -- was his first of the season, coming on his 109th plate appearance.
"I was just looking for a pitch to put in play," he said. "It happened to go out."
Saturday marked only his third start of June.
"It's been tough not playing," he said. "But it is what it is. I've been trying to keep my timing down in the bullpen, trying to stand in on some of our pitchers and stuff like that to keep the timing as game-like as possible."
Minnesota manufactured a run in the sixth, when Darin Mastroianni singled in Plouffe, who had doubled.
After De Vries' clean first inning, Butler's home run led off the second. He encountered more trouble after a Jeff Francoeur single and a one-out double by Salvador Perez. But De Vries -- who hadn't struck out more than four in any of his first three career starts -- reached back for two straight strikeouts to end the inning.
De Vries said the difference between Saturday and his previous three starts was "night and day." He posted a 1-1 record with a 4.20 ERA over those outings.
"The first two times out there, the emotions were very high," he said. "I knew they were going to be. Tonight, I felt a lot more comfortable out there and it helped out a lot."
He recorded four of his first six outs via punchout, attacking the strike zone early. He was seemingly a different pitcher from the one who gave up four runs in five innings against the Royals on June 4.
"I'll [tell] you this, he was much better this time than he was last time," Kansas City manager Ned Yost said. "He had good downhill on his fastball, was commanding four pitches, good curveball today."
The Twins entered the day last in the American League in home runs with 59. Their three home runs in Saturday night's game tied Minnesota's Target Field-high, which they previously accomplished six other times.
"The ball's been flying here," Gardenhire said. "We all know the big fence in right field -- we know that's going to eat a few balls up. But the ball was going along pretty good out there. It's been flying at home here with the temperatures like they've been."