White Sox center fielder Adam Engel broke a tie with an RBI triple in the seventh inning and scored with a headfirst slide on Yolmer Sanchez's sacrifice bunt one batter later. Tim Anderson added a two-run home run later in the inning to provide the final margin for the White Sox (45-68), who won their fourth straight game.
Still contending but sliding in a jumbled American League Central and wild-card race, Kansas City (57-58) lost its fifth straight and 10th time 12 games to fall under .500 for the first time since July 19.
Recalled from Triple-A Charlotte before the game, Lopez spaced two runs and four hits in six innings in his White Sox debut. He struck out six, walked three, and threw 68 of his 102 pitches for strikes in a no-decision. Lopez and fellow right-handers Dane Dunning and Lucas Giolito joined Chicago from the Washington Nationals in a December 2016 trade for Adam Eaton.
Royals left-hander Danny Duffy lost to the White Sox for the third time this season. Duffy fell to 7-8 after allowing five runs and seven hits in 6 1/3 innings, striking out eight and walking zero.
White Sox left-hander Aaron Bummer (1-2) earned his first major league win, striking out two in two innings of one-hit relief.
The White Sox took a 1-0 lead in the bottom of the first inning, as catcher Kevan Smith doubled to the gap in left-center field to score Anderson from first base. Chicago built on its lead one inning later behind a run-scoring groundout from Sanchez.
Designated hitter Mike Moustakas opened the scoring for the Royals with a solo home run against Lopez with one out in the fourth inning. He added a solo shot in the sixth inning, his 34th of the season.
The Royals scored on a wild pitch in the ninth inning, but Tyler Clippard recorded the final two outs to earn his third save of the season.
Anderson and Engel both had two hits for the White Sox. Alcides Escobar and Moustakas had two hits for the Royals.
NOTES: Moutakas delivered his third multi-home run game of the season and seventh of his career. His most recent came on July 22 against the White Sox. ... Royals starters have allowed 24 runs in 22 1/3 innings in the past five games. ... The White Sox recognized Royals RF Melky Cabrera with a video tribute before the second inning. Chicago traded Cabrera, with the White Sox since 2015, to Kansas City on July 30. Fans offered Cabrera a warm ovation when lineups were announced.