KANSAS CITY—Danny Duffy sat in the Kanas City clubhouse before Tuesday night’s game against the White Sox and listened to manager Ned Yost challenge his struggling ball club.The gist of Yost’s speech was that being 20 games under .500 was simply unacceptable. Small errors were leading to big innings, and the young Royals hadn’t been able to atone for them. Yost needed someone to step up and put together the kind of performance that could give the entire team a significant lift. Duffy took that talk to heart.The 22-year-old left-hander went seven stellar innings in his return from Triple-A Omaha, keeping Kansas City in the game long enough for Matt Treanor to deliver a go-ahead two-run single in the sixth inning. The Royals went on to defeat the Sox 4-2 and end a frustrating three-game slide. Melky Cabrera homered and Alcides Escobar drove in the other run for Kansas City, which came into the game batting .196 while scoring eight total runs during its skid. But with Duffy (2-4) out-pitching former Cy Young winner Jake Peavy (4-4), that meager offensive output proved to be just enough. Duffy hit the first batter he faced, walked the second on four pitches and allowed both to score. But he settled down after that shaky start and mowed through a lineup that Ozzie Guillen stacked with right-handed hitters for the express purpose of facing the left-handed rookie.Duffy needed 64 pitches to get through the first three innings — and 30 total over the next four. He allowed five hits and two walks while striking out six, matching the longest start of his blossoming big league career.Greg Holland pitched a perfect eighth inning for Kansas City, and Joakim Soria worked around a single in the ninth for his 10th consecutive save and 17th of the season. Peavy wound up taking the loss in what was still an encouraging performance. The two-time All-Star had allowed 14 earned runs in 16 1/3 innings over his last three starts, two of them losses and one against Kansas City. Peavy had said he’s been slow to bounce back after surgery about a year ago to repair a torn muscle under his right shoulder, but his command seemed to return against a struggling Royals lineup that has failed to score more than four runs each of its last seven games.Carlos Quentin and Alex Rios hit consecutive RBI singles in the first to stake Peavy to a 2-0 lead. His only blemish until the sixth inning came when Royals rookie Eric Hosmer singled in the second, Treanor hit a double and Escobar grounded out to drive home a run. Peavy set the Royals down in order in the fourth and fifth before finally cracking. Billy Butler singled with one out in the sixth and Jeff Francoeur doubled into the left-field corner to put runners on second and third. After a visit to the mound, Peavy intentionally walked Hosmer to load the bases for Treanor, who came through with a single up the middle to give Kansas City a 3-2 lead. Cabrera’s two-out homer in the seventh gave the bullpen a bit of breathing room.While the game turned into a defensive pitcher’s duel, it was a far from flawless performance. Both teams committed an error and there were numerous baserunning blunders. The most laughable came in the third inning, when Kansas City’s Alex Gordon got caught between second base and third. He tried to retreat to second and nearly ran into Cabrera, who had been on first and was trying to advance. The White Sox finally tracked down Gordon for the rare 2-4-5-6 caught stealing.

NOTES—The Royals sent LHP Everett Teaford to Omaha on Monday night to make room for Duffy. … White Sox 2B Gordon Beckham made just his second error in his last 100 games in the third inning. He also singled in the ninth to extend his hitting streak to a career best 10 games. … Royals 3B Mike Moustakas was 0 for 4, extending his hitless streak to 17 at-bats. … The White Sox sent LHP Hector Santiago to Double-A Birmingham after the game. John Danks is expected to come off the DL to start Wednesday night’s series finale.