Cubs manager Lou Piniella called Zambrano's outing "encouraging." Zambrano injured his leg running to first base, and he will test it doing baserunning drills on Thursday.
The right-hander is expected to join the Cubs' Class A Daytona team and pitch either Saturday or Sunday. Daytona plays at Clearwater from Thursday through Saturday, and at Dunedin from Sunday through Tuesday.
"With Zambrano, the news was good," Piniella said. "We've got him scheduled for San Diego next Friday [May 22]."
Third baseman Aramis Ramirez said his left shoulder still hurts after he dislocated it on Friday trying to make a diving stop during the game against the Milwaukee Brewers. When Ramirez was sidelined with a leg injury earlier this year, he was antsy after a few days. He's expected to be out four to six weeks because of the shoulder.
"This is worse because I'm going to be out for a while," said Ramirez, who expected to make some Minor League rehab outings.
In 2000, Ramirez suffered a partial dislocation of his left shoulder in late August and was sidelined for the rest of the season. That injury wasn't as severe, he said.
Considering all the injuries, the Cubs have the same record after 32 games this season that they did one year ago, 18-14.
"When you look at the problems we've had from a physical standpoint, and we've had some slow starts by some of our players, you have to feel fortunate at where you're at," Piniella said.
Carrie Muskat is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.