Athletics 8, Royals 3: Jon Lester pitched 6 2/3 solid innings in his Oakland debut as the host Athletics rolled past Kansas City.

Lester (11-7) gave up three runs and nine hits in his first start since being dealt from the Boston Red Sox prior to Thursday’s trading deadline. Oakland broke the game open with an eight-run fifth inning to move two games ahead of the Los Angeles Angels in the American League West.

Jonny Gomes, also acquired in the Lester deal that sent Yoenis Cespedes to Boston, contributed a two-run single. Jason Vargas (8-5) allowed seven runs and as many hits in 4 1/3 innings for Kansas City, which fell five games behind the Detroit Tigers in the American League Central.

Salvador Perez’s third-inning sacrifice fly gave the Royals an early lead and Vargas retired the first 12 batters he faced before Oakland blew the game open. Alberto Callaspo, Josh Reddick, Nick Punto and Jed Lowrie stroked run-scoring singles in the fifth, and Josh Donaldson drew a bases-loaded walk before Gomes singled home two runs with another scoring when Kansas City left fielder Alex Gordon misplayed the ball.

Lester tired in the seventh and gave up run-scoring singles to Norichika Aoki and Christian Colon before departing. Vargas was pitching for the first time since July 8 due to an appendectomy that prompted a stint on the disabled list.

GAME NOTEBOOK: Punto (hamstring) departed in the fifth inning after being injured while running the bases. … Vargas was activated prior to the game and 1B Eric Hosmer (broken hand) was placed on the disabled list. … Oakland CF Coco Crisp (neck) sat out for the sixth straight game.