The Cubs right-hander, who had to leave his Opening Day start because of cramps in his forearm, apparently has low levels of potassium.
"He's fine," Cubs manager Lou Piniella said of Zambrano, who is scheduled to make his next start Sunday against Houston. "His potassium level was a little low. I think that was the problem."
The Cubs have had Zambrano see specialists, and the medical staff has taken steps in order to keep him in games longer.
"It's something that shouldn't reoccur," Piniella said.
On Monday, Zambrano was pulled after 6 2/3 innings against the Milwaukee Brewers because of the cramps. What does he need to do?
"Drink water," Zambrano said.
Carrie Muskat is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.