Collin McHugh, claimed off waivers, pitched seven brilliant innings for Houston before giving way to Tony Sipp, added to the roster on May 2, who sat down four in a row and extended his scoreless-innings streak to 9 2/3 this season.
Alex Presley, another waiver claim, collected three hits for the second straight game and added a sacrifice fly.
"Those are huge pickups when you look at the impact that they've had on our ballclub," manager Bo Porter said after the game.
Their performances were not simply one-game mirages, but more a reflection of how Houston has concocted its four-game win streak and nine wins in its last 14 games.
McHugh spent two forgettable seasons with the Mets and Rockies, when he accumulated an 0-7 record in nine starts and an 8.69 ERA in 2012-13.
Nevertheless, the Astros saw something in him and were rewarded. In seven starts this season, he has a 2.80 ERA and a 0.978 WHIP.
McHugh flummoxed the Royals with his 12-to-6 curveball. Kansas City struck out seven times on the curve, and McHugh has allowed only one hit in 48 at-bats (25 strikeouts) against the pitch, according to brooksbaseball.net.
"When you've been around a little bit and seen a couple different organizations ... you kind of have a bit of a chip on your shoulder, you want to prove some people wrong," McHugh said after the game.
Sipp has been nearly unhittable thus far. Of the 31 batters he's faced this season, only one has a hit off him. He's walked just one batter, and it was intentionally.
Presley entered the three-game series with the Royals batting just .218, but his six hits helped his team claim the first two games, and his batting average now sits at a respectable .250.
Brian McTaggart is a reporter for MLB.com and writes an MLBlog, Tag's Lines. Follow @brianmctaggart on Twitter. Jackson Alexander is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.