The Red Sox were finally able to slow down the simmering Royals, but with a win on Sunday, Kansas City can still take its seventh straight series out of the All-Star break.
After losing 5-3 on Saturday, the Royals are 17-5 since the break and 4-2 through six games of a 10-game homestand.
But after winning the first two games of the series against the Red Sox, a series split would likely feel like a disappointment.
To avoid that outcome, Kansas City will send ace James Shields to the mound to face John Lackey in the finale.
Shields, who is 6-8 with a 3.36 ERA, is coming off one of his worst starts of the season. He gave up a season-high seven runs and three homers, including two in the first inning, against the Twins last Tuesday as the Royals were handed a 7-0 loss. The seven runs are the most Kansas City has surrendered in a game since the All-Star break.
"I didn't get off on the right foot today," Shields said after the loss. "Sometimes that's going to happen, but I've got to do a better job to finish the game off there."
The Red Sox lead the league with 24 series victories, but the best they can do on Sunday is a split.
Lackey has been one of the Red Sox's most consistent pitchers in 2013, which came as a bit of a surprise to many. Through 20 starts, he has a 3.21 ERA, but the Boston offense averages just 3.45 runs in support of the right-hander, the fifth-worst output for any starter in the American League. Consequently, Lackey's record is just 7-9.
He gave up two runs over six innings in his last start against the Astros, but took the loss after the Red Sox were shut out.
"I can only control how I pitch," Lackey said. "I had a pretty good breaking ball, got some swings and misses on that. It's frustrating. Hopefully next time things work out better."
Red Sox: Middlebrooks contributes in return
Will Middlebrooks wasted no time making an impact in his first game in the Red Sox lineup since June 20.
The third baseman clubbed a two-run single in the fourth inning and later came around to score. Overall, he went 2-for-4 with two runs and two RBIs in the 5-3 win over the Royals after being recalled from Triple-A Pawtucket earlier on Saturday.
Middlebrooks was the everyday third baseman entering the season, but he hit just .192 in 53 games and was demoted to Triple-A. He hit .269 with 10 homers and 34 RBIs while in the Minors and said the demotion taught him a lesson.
"You can't take all this for granted, because you can lose it real quick," Middlebrooks said. "I am going to take it day by day, have fun and help this team win games."
Royals: Perez could return Sunday
Royals manager Ned Yost is optimistic catcher Salvador Perez will be reinstated off the seven-day concussion disabled list on Sunday.
Perez sustained a low-grade concussion last Saturday in New York and as long as he passes the necessary tests, he'll likely make his return to the active roster.
"With Salvy there is a great chance he will come off [Sunday]," Yost said. "We don't know, we're keeping our fingers crossed that all the paperwork gets back."
• Left-hander Donnie Joseph threw two scoreless innings in relief on Saturday. He and Will Smith were recalled from Triple-A Omaha Saturday, though one of them will likely return to Omaha when Wade Davis returns from family emergency leave on Sunday.
• Red Sox shortstop Stephen Drew extended his season-high hit streak to 11 games after going 1-for-4 Saturday.
• Entering the 113th game of the season on Saturday, the Royals' starters owned a 3.92 ERA. Through 113 games last season, the starters possessed a 5.30 ERA, which ranked 28th in the Majors.
Michael Periatt is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.