OAKLAND, Calif. (AP) -- David Lough's indecision cost the Kansas City Royals.

The Royals' center fielder hesitated momentarily before breaking in to try and make a running catch on Derek Norris' short fly ball in the eighth inning.

The ball dropped in for a hit and then skipped past Lough for an error, taking with it any hopes Kansas City had of avoiding a sweep on the road.

That's how things are going these days for manager Ned Yost's team, which has lost 10 of 13 including three straight one-run defeats.

"Any time you lose a one-run game, especially when you have the lead in all three of them, it's a bit frustrating," Yost said after the Royals lost to the Oakland Athletics 4-3 on Sunday.

No one was feeling more down in Kansas City's clubhouse than Lough, who was pulled from the game shortly after his costly error helped the A's score the tying run.

Yoenis Cespedes then hit a leadoff home run in the eighth to lift Oakland to the win and complete a three-game sweep.

"If I would have went with my instincts I would have got to the ball," Lough said. "It was a hard hit ball and it was one of those where it could have sink on it. I kind of hesitated, pulled up and it took one of those sharp hops and just got by me on the top of my glove."

The loss dropped the Royals to 2-4 on their nine-game road trip despite a quality outing from starter Luis Mendoza.

Following gems by James Shields and Ervin Santana, Mendoza struck out four in six innings and didn't walk a batter for a second straight start but left with no-decision shortly after Lough's gaffe.

"I think the only hits that hurt me today were the bloopers," Mendoza said. "They did a good job of just making contact. I'm just trying to get outs as quick as possible and minimize the damage."

Alex Gordon matched his career high of four hits for Kansas City. The Royals have lost 10 of 13 and fallen back to .500 heading into a three-game series at Houston.

Oakland's first sweep of the Royals since 2008 didn't come easily.

The A's squeaked out a pair of 2-1 wins on Friday and Saturday, then had to sweat out another tight finish in the series finale.

Ryan Cook, pitching because closer Grant Balfour was unavailable, allowed two-out singles to Billy Butler and Eric Hosmer in the ninth. Mike Moustakas then worked a full count off Cook before grounding out to end the game.

Cespedes connected against Kelvin Herrera (2-4) for his eighth homer.

"He has a flair for that," Oakland manager Bob Melvin said of his Cuban slugger. "The guy's throwing 100 mph (and Cespedes) didn't really do anything mechanically to try to catch up to it. Just saw it and hit it."

Jerry Blevins (3-0) pitched one scoreless inning. Cook worked the ninth for his first save of the season.

Gordon hit an RBI single in the third, scored in the fifth and doubled in the seventh. Since moving to the third spot in the lineup on May 9, Gordon is batting .450 (18 for 40).

The Royals, who scored just two runs and stranded 11 baserunners in the first two games of this series, went up 2-0 when Chris Getz singled in Hosmer in the fourth. Hosmer added an RBI double in the fifth.

A's starter A.J. Griffin had command problems most of the day. He walked three and struck out five, but failed in his bid to become the second pitcher in Oakland history to reach 12 wins in his first 24 starts.

Josh Donaldson had a sacrifice fly in the Oakland fourth and Jed Lowrie had an RBI single in the fifth.

NOTES: Getz's single snapped an 0-for-16 slump. ... The Royals have scored 12 runs in their last seven games at the Coliseum while going 1-6. ... Gordon had 60 multi-hit games in 2012 but already has 20 in the Royals' first 40 games this season. He has nine career four-hit games. ... Kansas City RHP Jeremy Guthrie (5-1) pitches the series opener in Houston and is seeking to rebound from his first loss of the season.