"I think the last inning was the worst," Zambrano said. "I will take care of it."
This isn't the first time Zambrano has had to leave a game because of cramping. Once, it was related to too much computer use.
Zambrano, making his fourth Opening Day start, remained winless in season openers. He gave up three hits and walked one in 6 2/3 scoreless innings, striking out five.
"I felt good," Zambrano said. "It's too bad we lost the game, but we have 161 more to go."
Bill Hall doubled with one out in the Brewers' seventh, but Zambrano picked him off. The right-hander then seemed to have trouble flexing his right hand and was pulled from the game.
Carrie Muskat is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.