Manager Lou Piniella said the right-hander will likely pitch a simulated game Monday at the team's training complex in Mesa, Ariz., and his next stop would be Triple-A Iowa. Piniella said Zambrano could rejoin the Cubs during their six-game road trip that starts July 26.
Zambrano has been on the restricted list since June 29 following a three-game suspension for an emotional outburst aimed at teammates in the dugout of a June 25 game against the Chicago White Sox.
In addition to his suspension and time on the restricted list, Zambrano is believed to have undergone anger management therapy with doctors picked by Major League Baseball and Zambrano's agent.
Cubs general manager Jim Hendry said he was most concerned about Zambrano overextending himself upon his return.
"You want to make sure that you're sharp and you're ready when you get up here," Hendry said. "The health of the player is important. You don't rush it along, because when you get him up here he'll be over-amped a little bit. You have to prepare him for that."
Zambrano does not have to be moved off the restricted list for a minor league stint, only if he is recalled by the Cubs.
Zambrano, who was sent to the bullpen earlier in the season and is expected to return there, is 3-6 with a 5.66 ERA.
Bruce Levine covers the Cubs for ESPNChicago.com and ESPN 1000. The Associated Press contributed to this report.