"The calculus for us was, would we rather spend that $18 million on one year of Carlos and try to make it work with him here?" Epstein said. "Best-case scenario is that if it did work, he'd be leaving as a free agent at the end of the year.
"Or, if we had to spend that money anyway as a sunk cost, would we rather spend it on a 25-year-old who we can put in our rotation and control for three seasons? That made a lot more sense."
The Cubs' roller-coaster ride with Zambrano came to an end Thursday, when the team dealt the volatile right-hander to the Marlins for fellow righty Chris Volstad.
Zambrano, 30, waived both his no-trade clause and the $19.25 million option for 2013 to join good friend and Venezuelan countryman Ozzie Guillen, the new Marlins manager, who will try to keep the pitcher's emotions in check. Zambrano is the latest addition to the land of Oz, joining Heath Bell, Mark Buehrle and Jose Reyes.
Epstein was unable to find a trade partner until three days ago. Zambrano did not want to even discuss a trade during a face to face meeting with Epstein in November in Chicago.
But Epstein, who took over as president of baseball operations in late October, discovered a recurring theme in conversations with players and front-office executives regarding Zambrano. None of them trusted the mercurial pitcher to change his ways. Epstein had outlined steps Zambrano needed to take to earn his way back with the Cubs, but he said he was skeptical it could happen.
"Every player who I talked to articulated to me that Carlos had violated their trust," Epstein said. "When you're talking about physical altercations with teammates repeatedly, when you're talking about physically walking out on the team, it's very hard to have that player come back into the clubhouse and be trusted.
"I think, to be a good teammate, there has to be a certain degree of trust and accountability. Do I believe in second chances? Yes. Do I believe in third chances? Yes, in come cases -- even fourth chances. I think you have to be realistic about it and recognize that players don't dictate decisions like this, but you're trying to establish a certain sense of unity in the clubhouse and a certain sense of purpose, you have to have accountability and trust between the players."
The risk of having Zambrano become a distraction again was too high. His departure ends a tumultuous 11-year career in Chicago. The right-hander reached double digits in wins in six consecutive seasons, including an 18-13 campaign in 2007, and threw a no-hitter in '08. A three-time All-Star and three-time Silver Slugger winner, Zambrano was the Cubs' Opening Day starter for six straight years.
But he also frustrated the Cubs with his antics. There was the dugout fight with catcher Michael Barrett in 2007, the shouting match with Derrek Lee in 2010 which resulted in anger management therapy and his repeated blowups with umpires. In June, Zambrano blasted Carlos Marmol and the team after a loss to the Cardinals, saying players should be "embarrassed" and the Cubs were playing like a "Triple-A team." Said Zambrano then: "We stink."
On Aug. 12, Big Z made what turned out to be his last start for the Cubs. He served up five home runs to the Braves in that game, was ejected for throwing inside to Chipper Jones and left Turner Field. He told teammates he was retiring, then later recanted, saying he was embarrassed by what happened.
Zambrano was subsequently placed on the disqualified list. One week before the Aug. 12 game, the mercurial pitcher had hosted "Big Z Foundation Day" at Wrigley Field to raise money and help an orphanage in Guatemala.
Pitcher Kerry Wood wished Zambrano well with a tweet on Thursday, saying: "Best of luck to Big Z in Miami. Played together for 9 seasons. Wish him all the best!"
During the Winter Meetings, Guillen predicted Zambrano would win 14 to 16 games this season. Guillen said he communicated often with Zambrano but stressed then that they did not discuss the possibility of the right-hander coming to the Marlins. Both have done commercials together in Venezuela and helped each other's charities.
"We talk as a friend, we talk about what happened in the past, yes," Guillen said. "We talk about how better it's going to be, yes. We talk about what kind of pitcher he can be."
Zambrano's agent, Barry Praver, told Epstein that the pitcher would consider waiving the no-trade clause if he had a say in his next team and favored Miami.
The Marlins will essentially pay Volstad's salary in 2013 -- expected to be around $2.5 million -- which will be subtracted from the $18 million owed Zambrano.
Before agreeing to the deal, the Cubs and Zambrano settled a grievance filed after the right-hander's stint on the disqualified list. Zambrano will receive 24 days of salary out of his 30-day suspension, which is about $2.4 million.
Zambrano signed with the Cubs when he was 16 years old, and has a career 125-81 record and 3.61 ERA in 319 games. His 125 wins rank 15th in team history, and his 1,542 strikeouts are second. He will also help the Marlins at the plate -- Zambrano has 23 career homers, the most by a pitcher in Cubs history, and the most since Bob Gibson retired in 1975 with 24.
Now, he gets a fresh start in Miami.
"We're glad for him that he has a chance for a new start and a place where he can build new relationships and establish a new reputation for himself," Epstein said. "We think he has the chance to do that in Miami."
Carrie Muskat is a reporter for MLB.com. She writes a blog, Muskat Ramblings, and you can follow her on Twitter@CarrieMuskat. This story was not subject to the approval of Major League Baseball or its clubs.