Zambrano, injured May 3, will throw at Wrigley Field on Wednesday, then do some fielding drills and baserunning on Thursday. If he passes all the tests, he'll pitch for Daytona either Saturday or Sunday.
Zambrano will rejoin the Cubs in St. Louis next week, and the hope is that he will return to the rotation on May 22, when Chicago opens a three-game series in San Diego.
As for the Cubs' rotation this week, Ryan Dempster will start Thursday in the series finale against the Padres, to be followed by Randy Wells on Friday and Sean Marshall on Saturday against Houston. Wells is currently subbing in Zambrano's spot.
"When Zambrano comes back next week, we've got to look at what we do in the rotation," Cubs manager Lou Piniella said Tuesday. "One piece will stay in the rotation, the other to the bullpen."
That means either Marshall or Wells, who threw five scoreless innings in his first Major League start last Friday in Milwaukee, could stay in the rotation. Marshall is 1-2 with a 4.06 ERA in seven games, including five starts.
"I'm very comfortable with Marshall in the rotation -- I said that coming out of Spring Training," Piniella said.
The relievers have struggled, compiling a 5.40 ERA, but Piniella said he sees positives.
"It's looking better to me," he said. "That's the biggest chore we have here is to put together a solid bullpen that can function for the rest of the summer."
The Cubs have had to make adjustments as they try to deal with injuries to players such as Zambrano, Chad Fox (elbow) and Aramis Ramirez (shoulder). Fox had X-rays taken Monday of his right elbow and said the good news is that there was no major fracture.
"We thought we were going to see a train wreck when we got in there," he said.
However, the X-rays did show that one of the screws in his elbow is bent, and there could be a partial tear of the muscle.
"I think time is all we have right now," Fox said. "We'll see how it reacts on its own. After three surgeries, I don't know if a fourth surgery is what I'm looking forward to. If a fourth surgery will improve quality of life for me, I'll suck it up and go do it.
"I'm not going to make any retirement speeches. I'm worried about today. Two months, three months, six months down the road we'll see how it is."
He can be patient. Piniella can't.
"We do have a little different club from what we had coming out of Spring Training," Piniella said. "The injuries haven't helped and a couple of our guys have gotten off to slower starts, but you have to let them play. Towards the tail end of our lineup, we can inject a little speed and hopefully run a little more back there.
"The important thing is we pitch well and defend well. That will give us ample opportunities to win baseball games."
Piniella would like to see the Cubs be more selective with men in scoring position.
"We make easy outs, and that's got to get better," he said. "That's not only our team, but every Major League team. When you struggle in that department it makes it difficult to score runs."
Carrie Muskat is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.