OAKLAND, CALIF. ? Abraham Nðñez already has a plan for the ball from his first career grand slam: It will be a gift for his father, Amado, the man who pushed him to play baseball.

Nðñez hit a grand slam for his first home run of the season, spoiling Mark Mulder’s bid to become the majors’ first 16-game winner and leading the Kansas City Royals over the Oakland Athletics, 10-3, Friday night.

Nðñez connected on full-count with two outs in the sixth to break a scoreless tie. It was only his second career homer and his first grand slam. The four RBIs also were a career best.

“I’m never going to forget that. It was my first one,” Nðñez said. “I knew I hit it good and that it had a chance.”

A fan threw the ball back onto the field, which allowed Nðñez to leave with the souvenir.

John Buck, another rookie, also hit a grand slam for the Royals, the first of his career and the first time in club history the team has had two in a game — which ties a major league record. It marked the second time the A’s have allowed two grand slams in a game and the first since 1986 against California.

Buck snapped an 0-for-21 streak with his shot to center and the Royals ended a 10-game losing streak to the A’s, which included the first six meetings this season.

According to The Elias Sports Bureau, Buck and Nðñez are the first rookie teammates to hit grand slams in the same game since the rookie rule went into effect in 1957.

While Nðñez’s reward was the ball, Buck earned himself another day in the lineup today, when manager Tony Pena originally had planned to rest the catcher.

“It was one of those at-bats where I went up there and saw the first pitch and told myself, ‘I saw it good, hit it up the middle,'” Buck said. “When you’re struggling, you tend to think too much.”

Kansas City starter Mike Wood (2-4) — yet another rookie to make a big contribution — pitched six strong innings to win for the first time since June 29, a span of eight starts.

It was his first career start against the A’s, who selected him in the 10th round of the 2001 draft then dealt him June 24 in a three-team trade that sent standout center fielder Carlos Beltran from the Royals to the Astros and brought closer Octavio Dotel to Oakland from Houston. Wood had lost his last four decisions. Buck also was part of the swap.

Wood was bothered by stiffness in his lower back on the flight to Oakland, but it wasn’t enough to keep him from pitching.

“It’s very rewarding,” he said of beating his former franchise. “Maybe there’s a little regret they let me go. Ever since they drafted me, it was my dream to pitch for those guys. … My teammates were pumped for me today.”

Joe Randa added a two-run homer in the eighth off Mulder, Randa’s fourth of the season.

Mulder (15-4) didn’t allow a baserunner past first until the sixth.

Kansas City’s David DeJesus singled with one out in the sixth to extend his hitting streak to 14 games, a record by a Royals rookie. He advanced to third on Mike Sweeney’s single to right two batters later. Ken Harvey walked to load the bases.

Mulder then allowed Nðñez’s grand slam, a towering shot over the center-field wall.

“I made one bad pitch really,” Mulder said. “It kind of lost the game for us, but otherwise I felt really good.”

The A’s made things interesting in the bottom half when they loaded the bases against Wood. But Bobby Crosby was thrown out at home on Eric Chavez’s hard roller to first. Scott Hatteberg followed with a sharp single to make it 4-1, but Mark McLemore was thrown out trying to score on the play when DeJesus made a perfect throw home from center to Buck to save a run.