"His actions last night were totally intolerable," Cubs general manager Jim Hendry said. "This was the most stringent penalty we could enforce without a release."
After giving up five home runs in a 10-4 loss to the Atlanta Braves and getting ejected for throwing at Chipper Jones on Friday, Zambrano cleaned out his locker and told trainers and clubhouse people during the game that he was "retiring."
Zambrano's agent Barry Praver told ESPN The Magazine's Buster Olney that the Cubs were told within two hours after Friday's game that Zambrano "definitely" wasn't retiring. Praver said Zambrano made private emotional remarks to club staff and returned his things to his locker late Friday night.
Praver told ESPNChicago.com that the Major League Baseball Players Association will file a grievance on Monday due to the severity of the punishment.
"His actions last night are very detrimental to his teammates," Hendry said. "There's not much worse than running out on your teammates and announcing your retirement."
Hendry said he apologized to Braves general manager Frank Wren for the actions by Zambrano, which tarnished former manager Bobby Cox's night. The Braves retired Cox's No. 6 before the game.
Zambrano was ejected by plate umpire Tim Timmons in the fifth inning after throwing two inside pitches to Jones, the second going all the way to the backstop. The brushback pitches followed homers by Freddie Freeman and Dan Uggla.
"It was uncalled for, the pitch to Chipper Jones," Hendry said.
"I feel that anything at all to detract from Bobby Cox's night other than usual competition is totally intolerable."
Asked if he knew where Zambrano was on Saturday, Hendry said, "I have no idea."
Jones said Hendry's comments were "a class move. I appreciated it."
Added Jones: "I like Carlos. I've always liked Carlos. He's an intense competitor. Unfortunately, sometimes that hurts him."
Cubs pitcher Ryan Dempster wasn't so understanding.
"He's made his bed. Let him sleep in it," Dempster said.
"It's not like it's something new."
Outfielder Marlon Byrd said he talked with Zambrano.
"He said that he's doing better today," Byrd said. "That's it."
Asked about Zambrano being placed on the disqualified list, Byrd said: "That's business. They have to do what they have to do."
Cubs third baseman Aramis Ramirez said Zambrano would be welcomed back by his teammates, but only if he made changes.
"If he changes his attitude, he's more than welcome," Ramirez said.
"He's got to think a little bit more. He's one man. It's not just one time. A lot of people have tried to help him. He won't let them."
The Cubs refused to be distracted by Zambrano's situation Saturday night, beating Atlanta 8-4. Manager Mike Quade said he wasn't surprised when his team responded to the controversy with a win.
"You know what? I'm never surprised at these guys," Quade said. "They just come to the park and play.
"They just go about their business. And that's a good thing. No distractions. Let's just play."
Cubs pitching coach Mark Riggins, one of the last team members to speak to Zambrano during an in-game visit to the mound, said he didn't see Zambrano's actions coming.
"It shocked me that happened last night," Riggins said on ESPN 1000's "Talkin' Baseball" radio show on Saturday. "For a player to leave a team, that's kind of just leaving us out there hanging and it seems like it's about him and it's not about the team.
"You just can't let your emotions get that far. We're professional people. We're supposed to be able to handle this, whatever comes our way. It's just disappointing. And we all get embarrassed and it's how we handle those situations, I think, (that) shows the character we have."
Speaking as "a manager and his friend," White Sox boss Ozzie Guillen said Zambrano is in "a very bad and very sad situation."
"It's tough on how a manager would handle that because he's very intense about respect, loyalty," Guillen said Saturday in a pregame talk with media. "On the other side, this kid has a lot of pride. This kid's embarrassed. This kid wants to be good, and I think he feels like he's not doing his job.''
Zambrano's track record of abnormal behavior is long and well-documented.
He bashed teammates on June 4 in St. Louis, calling them "Triple-A players" after the team lost a 10-inning game on an Albert Pujols walk-off home run. He apologized to the entire team the following day in Cincinnati.
On June 25, 2010, Zambrano had a dugout blowup with then-Cubs first baseman Derrek Lee at US Cellular field. Zambrano was suspended for two days before being placed on baseball's restricted list for six weeks. After he returned to the team on Aug. 8, he went 8-0 in 11 starts. Zambrano also went through eight months of anger-management sessions after the incident with Lee.
In 2007, Zambrano signed a deal adding $91.5 million over five seasons through 2012. He was to earn $17.85 million this season and $18 million in 2012.
Zambrano is 9-7 with a 4.82 ERA in 24 starts for the Cubs this season.
Zambrano's name was mentioned in trade rumors before the July 31 deadline. He said on July 28 he wanted to remain with the Cubs.
"I do want to stay here but at the same point I want this team to make some changes," Zambrano said. "If we want to win here, we need to make some changes. If I have to go, I have to go but I still have the Cubs in my heart."
Casey Coleman is likely to be called up from Triple-A Iowa to start Wednesday in Zambrano's spot. The team will need a starting pitcher for Zambrano's next scheduled turn in the rotation Wednesday at Houston.
Bruce Levine covers the Cubs for ESPNChicago.com and ESPN 1000. Information from The Associated Press was used in this report.