OAKLAND -- Someone wondered before the first pitch what Oakland Athletics' manager Bob Melvin was going to do about Yoenis Cespedes.
The second-year major-leaguer from Cuba was hitting below the dreaded "Mendoza Line" of .200, at .198. Or as the players say, he's on the wrong interstate, I-98.
Melvin shrugged off the question. "He's fine," the manager said. "He's just an aggressive swinger. He's staying, because when he's in the lineup he takes the pressure off everybody. He's so important."
Cespedes certainly was Sunday. Leading off the eighth inning Sunday, he drove the second pitch of Kansas City Royals reliever Kelvin Herrera over the left field fence, breaking a tie and giving Oakland a 4-3 win and a sweep of the three-game weekend series.
"It was a good pitch, finally," said Herrera, who had just taken over. He was tagged for his eighth home run of the season. "I made the good pitch, but he jumped on the fastball. I threw it right where I wanted it, down and away, but he just hit it. He's got power, and he made good contact."
Kansas City lost by one run in all three games at O.co Coliseum, the first two by scores of 2-1.
"Our starting pitcher did so well," Royals manager Ned Yost said of Luis Mendoza. "We've been struggling to score runs. We finally put some runs on the board, and we lose. That's baseball."
After an 11-7 start, the Royals have slipped to 20-20. The A's, meanwhile, pulled above .500 at 23-22.
Aside from Cespedes' eighth home run of the year, the key moment Sunday was a misplay by Royals center fielder David Lough. Playing only his third game since being called up, Lough started to go after a line drive by Derek Norris that opened the bottom of the seventh. Then he stopped. Then he started again.
The ball bounced alongside Lough then rolled to the fence, a single and a two-base error. Norris scored on a one-out sacrifice fly by Coco Crisp off Bruce Chen to bring the A's, who had trailed since the third inning, into a 3-3 tie.
"It was a hard-hit ball," Lough said. "My instinct was to go after it. It had some sink. When I went for it, it bounced past. I wish I had followed my instincts."
Melvin certainly used his instincts. Last season's AL Manager of the Year knows Cespedes is a free swinger, and he also knows Cespedes never gets down on himself. Thus, whatever Cespedes' average -- it's now up to .208 -- he'll be batting third.
"He wants to be the guy," Oakland right-hander A.J. Griffin said of Cespedes.
Griffin went six innings and allowed seven hits and three runs. He was not involved in the decision.
Hideki Okajima and Jerry Blevins (3-0) each pitched a scoreless inning after Griffin's exit.
After Cespedes' homer, Ryan Cook took over in the ninth and retired the first two batters before Billy Butler and Eric Hosmer singled. Butler moved to third on Hosmer's hit, and Hosmer took second on defensive indifference. Cook got Mike Moustakas to ground out, getting the save and an ovation from the majority of the 20,387 fans at Coliseum.
"I'm throwing the best fastball I have all year," said Cook, who got his first save of the season after collecting 14 last year.
It was that sort of series for Oakland. And Kansas City. The A's scored only eight runs total in the three games and won each.
The Royals' Alex Gordon had the ninth four-hit game of his career, three singles and a double, and now is batting .343. Even so, Kansas City remained stymied.
Mendoza held the A's to three runs (two earned) in six-plus innings.
"He's sneaky fast," Melvin said. "He has a boring fastball."
However, Lough's error allowed the A's to even the game and set the stage for Cespedes' heroics.
"A guy like Cespedes can turn things around on one pitch," Melvin said. "Sometimes you get frustrated. We all do. That's why you stay with it."
NOTES: The A's are now 6-1 in games decided in the last at bat. ... Oakland and Kansas City both left immediately after the finish for games in Texas, the A's against the Rangers, the Royals at Houston. ... Oakland 3B Josh Donaldson had a career-high, seven-game hitting streak stopped. He went 0-for-3 plus the sacrifice fly. ... Dating back to the last game Kansas City played at Oakland in 2011, the Royals have been able to score only 12 runs over the past seven games a O.co Coliseum and lost six out of seven. ... Melvin said the return to the lineup of Crisp -- who Sunday was the designated hitter -- invigorates the team not matter what he does. ... The A's lead the majors in walks with 179, even though they didn't get any Sunday.