Zambrano has not pitched in a game since Aug. 12. The 30-year-old veteran was ejected from that game in Atlanta, then left the ballpark, saying he was retiring. He has since said that the retirement comment was made out of frustration after he served up five home runs in that start. The right-hander was placed on the 30-day restricted list and did not rejoin the Cubs.
Zambrano tuned up for Sunday's start with a 40-pitch outing on Tuesday.
"I think it's a good thing [that he's pitching], under the circumstances," said Cubs president of baseball operations Theo Epstein. "He probably needs the innings. It could be good for his state of mind to get out there and perform."
Epstein has talked to Zambrano's agent, Barry Praver, and would like to talk to the pitcher next week, if possible.