Greinke was wearing the jersey the Brewers plan to wear on Sunday to celebrate German heritage in Wisconsin. Instead of saying "Brewers" on the front, it says "Bierbrauer," the German translation of the team nickname.
Greinke was unavailable for comment after the game, but manager Ron Roenicke said his star right-hander was wearing a fleece over his jersey during the game, so no one noticed it was the wrong uniform. When Roenicke called on him to bunt, he pulled the fleece off, grabbed a bat and went out to hit.
"I had no idea," Roenicke said. "It was blue, and that's all it looked like to me. I didn't know until one of the guys said something. He didn't know [either]."
Greinke put down a perfect bunt to advance Jonathan Lucroy to second for his sixth sacrifice of the year.
"If he bunts like that, he can wear what he wants," Roenicke said. "He's a very good bunter."
It is against Major League rules for one player to wear a different jersey than the rest of his teammates.
"All they do is send you a memo saying don't do it again," Roenicke said. "If you do it again, they'll fine you."
Greinke gave up only two runs in 7 2/3 innings in the Brewers' 7-2 victory over the Pirates on Friday night.
Joe DiGiovanni is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.