Zambrano was a bundle of emotions at times, walking way too many and behaving badly. But he also made the National League All-Star team three times and finished in the top five in the NL Cy Young Award balloting three times in a four-year stretch.
Among active pitchers, Zambrano is 16th in ERA, ahead of Chris Carpenter, Cliff Lee and Zack Greinke. His 7.6 strikeouts per nine innings is 23rd among active pitchers.
Zambrano started six Opening Days for the Cubs and was one of the players fans believed would finally lead them to a World Series. With the Marlins, he's being asked to fit in at the back of the rotation.
The thing the Marlins just can't know is whether Zambrano can hold himself together long enough to take advantage of all that talent. The Cubs, who are paying $15 million of his $18 million salary, apparently doubt it.
The Marlins are hoping Zambrano's friendship with manager Ozzie Guillen will assist the pitcher in controlling his temper. If that happens, the team will have gotten one of baseball's best bargains.
So far, so good. Zambrano showed up at Spring Training around 15 pounds lighter than this season, and even though he has struggled badly with his command, he has behaved himself and thrown the ball hard.
"He's been throwing the ball very good," Guillen said. "I expect him to have a good season. I always say, 'Whatever happened in the past, stays in the past.' This is a new year. He can open a new book. He's very happy here, and hopefully, it'll work for him."
At times, Zambrano sounds almost wistful in his desire to regain his greatness. At other times, some of the old testiness surfaces.
"I'm not anxious," he said. "I just want to do my job. Hopefully, we can talk at the end of the season. I just want to enjoy this game and start from there."
Zambrano has walked 14 in 17 2/3 spring innings as he enters Monday's final spring start against the Yankees at Marlins Park.
"The walks have been killing me this spring," he said. "Like I said, this is Spring Training. I feel good. I've been throwing the ball hard. I've thrown some real good sinkers. Spring Training is to work on what you have to work on. The season is what counts, and I feel I'm throwing the ball good."
When Zambrano pressed on the other stuff, he waves off the questions, saying he has answered the same stuff too many times already.
"The last few years I haven't pitched good," he said. "Ozzie is one of the smartest guys I've ever met, and he's a good manager. He gives you confidence. If you play right for him, he has your back. He'll be there for you. I just want to enjoy this game and start from there."
Some of the people who knew Zambrano best in Chicago are rooting for him. They've seen all sides of him and believe he has a good heart. They point to his charitable work and to his recognition that he has been his own worst enemy.
They also point out that Zambrano has begun other Spring Trainings by vowing to control his emotions better, only to let things get away from him during the heat of a season. Still, Zambrano is one of the most interesting gambles any team took this offseason and one of the ones that'll be worth watching play out.