KANSAS CITY -- Zack Greinke added another nice chapter to the Royals' pitching story so far this season.

After Greinke pitched eight innings of a 4-0 victory over the New York Yankees on Wednesday night, the Royals' staff ERA of 2.25 was the best in the Major Leagues.

Greinke did not let the rain that fell constantly after the second inning bother his work.

"Zack did a good job," catcher John Buck said. "There was a point there when he'd throw a pitch and I'd throw it back to him and the ball was already wet. There was a point there when it was really coming down. And for him to stay in there and be so consistent and battle through, that was a good job on his part."

Although Greinke felt strong enough to have pitched the ninth inning, manager Trey Hillman opted to go with reliever Yasuhiko Yabuta and, after he encountered a jam, Jimmy Gobble.

Greinke threw 107 pitches, including 73 strikes.

"I feel like I could've [pitched the ninth], but a pitch count's a pitch count, and the bullpen's been doing great," Greinke said. "I can't complain with how he handled the situation."

In fact, the Yabuta-Gobble ninth inning gave the Royals' bullpen a 0.82 ERA (two runs in 22 innings).

Greinke is 2-0 with a 0.60 ERA this season.

"He located his pitches pretty well," Hillman said. "He climbed the ladder with a difficult-to-track fastball after he'd thrown some slower pitches, and he was very effective."

Greinke handled the adverse conditions with aplomb.

"It didn't affect my footing at all," he said. "Even when it looked bad on the pitcher's mound, it really wasn't that bad pitching. But I did have a hard time with the grip. It is a little tougher with the raindrops."

Not all that tough, apparently.