Dallas Keuchel pitched five shutout innings Sunday for the Chicago White Sox but left after warming up for the sixth because of lower back stiffness.
The Sox said Keuchel's status is day to day.
He allowed two hits, struck out two and threw just 49 pitches in an 8-2 victory against the Kansas City Royals at Kauffman Stadium.
Edwin Encarnacion hit a three-run homer as the Sox (26-15) completed a four-game sweep in Kansas City, Mo. They maintained their half-game lead over the Cleveland Indians in the American League Central.
Encarnacion went 2-for-5 with four RBIs. Yolmer Sanchez doubled twice and scored two runs, and Yasmani Grandal had two hits and two RBIs.
Sanchez began the third with a double, his first hit since returning to the Sox on Aug. 31. Grandal drove him home with a one-out single to right.
Luis Robert reached in the sixth with a two-out walk. He stole second and scored on a double to left-center by Nomar Mazara.
Jose Abreu extended his hitting streak to 20 games with a single in the seventh. He scored on Encarnacion's eighth homer.
One of the Royals' best chances against Keuchel came in the fourth. Danny Mendick made a throwing error, and Hunter Dozier ended up on second to start the inning.
Mendick atoned with two outs, ranging to his right and throwing to first to get Bubba Starling, who was called out on a close play.
Jimmy Cordero replaced Keuchel in the sixth. The Royals placed runners on the corners with two outs, but Cordero struck out Ryan McBroom to end the inning.
Royals right fielder Edward Olivares hit a two-run homer off Steve Cishek in the seventh, cutting the Sox lead to three.
The Sox responded with three in the eighth. Sanchez began the inning with a double, and Grandal knocked him in with a one-out double. Encarnacion had an RBI single and Eloy Jimenez an RBI double.
The Sox completed the season series against the Royals with a 9-1 record. They begin a two-game series against the Pirates on Tuesday in Pittsburgh.
