Zambrano had been scheduled to start Sunday's game against the Arizona Diamondbacks, but the start of the game was delayed by rain and the Cubs have decided to scratch Zambrano from the lineup. The Diamondbacks decided to scratch starter Randy Johnson as well.
Zambrano said he had his shoes and gloves approved by league officials, the Chicago Tribune reported Sunday.
"This will be for breast cancer," said Zambrano. "It is a great thing; anything I can do for the people."
Zambrano said he had wanted to dedicate Sunday's game to all mothers worldwide, particularly his mom in Venezuela.