KANSAS CITY, Mo. -- Chris Sale was pleased with the victory, but was not happy he did not finish what he started.
Sale (9-3) increased his major league-leading strikeout total to 146. He has struck out 10 or more in 10 starts. The last Red Sox player with 10 or more such starts prior to the All-Star break was Pedro Martinez with 11 in 1999.
"A little frustrating," Sale said of not throwing back-to-back complete-games. "But at the end of the day we got the win. We're good."
When Sale gave up two runs on two hits and a walk in the ninth with his pitch count reaching 110 on a hot humid evening, manager John Farrell summoned Fernando Abad to get the final two outs.
"I'll never settle," Sale said. "When you start settling, you get complacent. When you get complacent, you suck."
Sale dominated the Royals, retiring 19 in a row after Alcides Escobar lead off third inning single. It was Escobar's 1,000th career hit as a Royal.
"We've seen him enough to realize how good he is," Royals third baseman Mike Moustakas said. "He locates all his pitches, throws hard and has great stuff. You just try to put the ball in play, try not to get to two strikes. I was able to do that in that first at-bat."
It was no sale for the Kansas City hitters.
"He was good," Royals manager Ned Yost said. "He threw more changeups tonight. His changeup was really good but so was his fastball and slider."
"We scored a bunch of runs and that takes a lot of pressure off a pitcher," Sale said.
The victory moved the Red Sox (40-31) into first place in the American League East, a half-game in front of the New York Yankees, who have lost seven straight. Boston is 19-10 since May 21. It is the first time this season the Red Sox are in sole possession of first place.
Sale prevented the Royals (34-36) from reaching .500 for the first time since April 19 when they were 7-7.
The Red Sox added three runs in the sixth with Leon scoring on a Young double. Bogaerts drove in two more runs with a single.
Jorge Bonifacio, who struck out in his first three at-bats against Sale, homered with Whit Merrifield aboard in a two-run Kansas City ninth.
Mike Moustakas hit his 100th career home run in the second, driving a Sale 1-0 pitch 440 feet to right, giving the Royals a 1-0 lead.
"I wish it would have came in a win for sure, but it's definitely pretty cool to hit a hundred home runs in the major leagues," Moustakas said. "It's definitely pretty special."
The Red Sox tied it in the third with Mookie Betts' single scoring Devin Marrero, who led off the inning with a double.
Royals rookie left-hander Matt Strahm (2-4) failed to make it out of the fourth inning, facing four batters in that frame and all scored, as the Red Sox seized a 5-1 advantage.
Jackie Bradley Jr. opened it with a single and scored when Sam Travis drilled a double to left. After Josh Rutledge beat out an infield single to Moustakas, Strahm uncorked a wild pitch as Travis and Rutledge each moved up 90 feet. Leon got both home with a double and finished Strahm's evening after 75 pitches.
"Just making quality two-strike pitches was my nemesis today," Strahm said. "I thought I had good command. I just wasn't getting it down. I was throwing all four pitches for strikes early in the counts and just couldn't finish them."
Scott Alexander replaced Strahm and promptly threw a wild pitch, advancing Leon to third. Marrero's sacrifice fly to center fielder Lorenzo Cain brought Leon home.
Strahm's final line was five runs on seven hits, a walk and a wild pitch. He faced 17 batters.
NOTES: The Red Sox made four roster moves. They placed 3B Pablo Sanchez on the disabled list with an ear infection. They optioned RHP Austin Maddox to Triple-A Pawtucket. They recalled 1B Sam Travis and 3B Deven Marrero from Pawtucket and both were immediately inserted into the lineup. ... Royals LHP Danny Duffy threw to hitters before the game for the first time since going on the disabled list May 30 with a right oblique strain. ... Royals RHP Nathan Karns will throw Wednesday for the first time since having a setback in a June 10 bullpen in San Diego. ... Royals prospect RHP Luke Farrell, the son of Red Sox manager John Farrell, allowed one run and three hits over eight innings, while striking out nine and walking none as Triple-A Omaha beat Iowa 5-1. ... Red Sox LHP Drew Pomeranz and Royals RHP Ian Kennedy are the Wednesday probables in the series finale.