OAKLAND, CALIF. ? The Kansas City Royals are as baffled as Oakland that they stole two of three from the AL West leader — with A’s aces Mark Mulder and Barry Zito on the mound, no less.

Joe Randa hit a three-run double with two outs in the seventh inning to spoil a strong start by Zito and lead the Royals over the A’s, 6-1, Sunday.

“We didn’t really generate anything all day off him, and we got pretty lucky,” Randa said. “I was able to get a pitch to handle and do something with it.”

David DeJesus singled leading off the ninth to extend his hitting streak to 15 games, a Royals rookie record that matches the club’s longest this year.

DeJesus struck out twice, walked and was hit by a pitch.

Kansas City also won, 10-3, Friday night in a game that featured two grand slams off Mulder, a 15-game winner who was the AL’s winning pitcher in the All-Star game. It marks the first time in a month the Royals have won a road series, and the first time this season the A’s have lost back-to-back home series.

Oakland lost to of three against Detroit last week.

“Disappointing, very disappointing,” manager Ken Macha said.

Zack Greinke (5-9), who made his major-league debut on May 22 in Oakland, won for the first time in seven road starts this season — and the Royals earned just their sixth victory in their last 26 games away from Kauffman Stadium.

Kansas City's David DeJesus is greeted in the dugout after scoring in the seventh inning. DeJesus extended his hitting streak to 15 games Sunday at Oakland, Calif., and the Royals won, 6-1.

Greinke gave up one run on six hits in seven strong innings, struck out four and walked one.

Royals manager Tony Pena considered the weekend a confidence boost for his club.

“No question about it,” he said. “Especially when you’re playing all those young kids, it’s good for them to know how to win.”

Zito held the Royals scoreless until the seventh, when he issued a one-out walk to Alberto Castillo and Ruben Gotay reached on a fielder’s choice. Andres Blanco followed with a double to chase Zito.

The left-hander received a standing ovation when he hustled off the field after giving way to Ricardo Rincon.

Rincon hit DeJesus with a pitch on a full count to load the bases, then Justin Duchscherer relieved and gave up Randa’s double.

Duchscherer gave up a two-run single to Gotay in the eighth, and Abraham Nunez had an RBI single in the ninth.

Zito (8-9) matched his season high with nine strikeouts. It was his longest scoreless effort since June 3, when he didn’t allow a run in seven innings of the A’s 3-2, 11-inning victory against Toronto.

“I had a lot of my stuff down in the zone today, which is good,” Zito said. “I felt good all day, and then they brought bullpen in. We have confidence in the bullpen. It’s just one of those days.”

Zito retired the side in order in the first, fourth and fifth innings. He worked out of a second-inning jam and another in the sixth.

DeJesus drew a leadoff walk, then stole second on Randa’s strikeout. DeJesus advanced to third on an infield single by Ken Harvey, but Zito got Nunez to fly out to end the inning.

Eric Byrnes drove in Oakland’s run with a single in the fourth, extending his hitting streak to 10 games. But there weren’t many other offensive bright spots for Oakland.