Kansas City, Mo. ? Zack Greinke had his 95-mph fastball working Wednesday night and it wasn’t even his best pitch.

It was his 50-mph curveball that had the Detroit Tigers shaking their heads after the rookie right-hander pitched Kansas City to a 1-0 victory Wednesday night.

“I don’t know how you can throw that for a strike,” said Detroit starter Mike Maroth, who had one of his finest outings nullified by the 20-year-old Greinke.

Greinke, who does not turn 21 until Oct. 21, was perfect through five innings before Craig Monroe singled to lead off the sixth.

He dazzled the Tigers with an assortment of fastballs, breaking balls, sliders and changeups — all thrown at varying speeds for strikes.

\He gave up three hits in seven innings, striking out five without walking a batter.

He went as high as 95 on his fastball and as low as 50 on a special curveball he learned from Dave LaRoche, the Royals’ Triple-A pitching coach.

“We worked on it a little bit but he said, ‘You have to promise me you won’t ever throw it in a game,'” said Greinke (7-9). “I said I’m sorry, I’m going to use it some day.

“I just lobbed it in there with spin.”

Abraham Nunez, another rookie, singled home Joe Randa in the fourth with the Royals’ only run off Maroth (10-10), and Kansas City handed the Tigers their sixth loss in seven games.

Jeremy Affeldt pitched a perfect ninth for his ninth save in 12 chances for the Royals, who won for just the third time in 11 games.

Maroth retired the first eight batters until Alexis Gomez bunted safely with two out in the third.

Maroth struck out a career-high eight batters over eight innings.

“Any time you get a loss it’s hard to look at it as your best game,” said Maroth. “Zack was throwing great. He had great command of his pitches and he knew what he was doing.”

Greinke, who gave up a team record-tying four home runs to Seattle in his previous start, surrendered consecutive singles to Ivan Rodriguez and Dmitri Young with one out in the seventh but then coaxed Carlos Guillen to ground into a 6-4-3 double play.

“Greinke is something special,” said Royals catcher Alberto Castillo. “Kansas City should be very happy to have that kid. And I’m happy to catch him.”

Randa singled with one out in the fourth, went to second on Stairs’ single and scored on Nunez’s single to left.

The Tigers had runners at second and third with two out in the eighth but Gomez made a fine catch running in of Omar Infante’s sinking liner.

A knuckleball may be the next new pitch for Greinke.

“I’ve worked on it but it’s not any good,” Greinke said. “Once it becomes a good pitch I might use it. But it’s garbage right now.”

Tiger manager Alan Trammell had never seen a pitcher whose velocity varied by 45 mph.

“For a kid, that’s not normal to have great control and great command,” Trammell said. “It looks like he’s the real deal. Maroth was not bad either.”

Notes: Detroit RHP Jason Johnson had a mild diabetic reaction during batting practice and was treated by the trainer. He later returned to the field. … The three-game series was the Royals’ shortest homestand of the season. … The Royals lost 19 games in August and committed a major league-high 31 errors. … Since Calvin Pickering homered in the fifth inning on Monday, the Royals have hit 27 straight singles without an extra-base hit.