He's brash, and he boasted this spring he would win the Cy Young Award and World Series.
He wants things done his way, and he scuffled with catcher Michael Barrett in the dugout in June.
In the end, he won a career-high 18 games for the Chicago Cubs, and on Wednesday, he'll be pitching Game 1 of the National League Division Series against the Arizona Diamondbacks.
But there are some things you probably don't know about the Cubs pitcher.
Zambrano is ambidextrous, and some people think the right-hander could throw just as well from the other side of the pitching rubber.
"If you put a glove on his right hand and watched him throw left-handed, you'd think he was left-handed," said Cubs player development director Oneri Fleita.
Don't expect Zambrano to be experimenting in the NLDS, the Cubs' first trip to the postseason since 2003. That year, he was 0-1 in three postseason starts. This time?
"I'm ready, I'm excited," Zambrano said. "After I went to the playoffs in '03, I got thirsty and hungry for that first game. Now that I have more experience in the big leagues, I'm ready for the playoffs."
In Spring Training, Zambrano, 26, boldly predicted he would win pitching's top award as well as hoist a World Series trophy in October. Hector Ortega, one of the Cubs' Minor League coaches and a scout in Venezuela, wasn't surprised by the bold statements.
"He knows what he has to do," said Ortega, who has known Zambrano since he was 15. "Cy Young is one of the things he has on his mind. Win the World Series is first, Cy Young is second. That's the type of guy he is. He's a team player."
It didn't look that way on June 1, when the Cubs were playing host to the Atlanta Braves at Wrigley Field. The Braves had just scored five runs in the fifth inning, including one after a combination passed ball and throwing error by Barrett, then the Cubs' regular catcher. After the players came off the field, Zambrano confronted Barrett in the dugout, pointed to his head -- he asked, "Are you out of your mind?" -- and then took a swing at the catcher.
Cubs manager Lou Piniella and others had to separate the two. Zambrano was lifted for a pinch-hitter, and Barrett was supposed to stay in the game. But he had gone into the clubhouse, trying to make peace, and the two got into another fight. Barrett ended up with a black eye and cut lip, and he was eventually traded.
"It's all my fault," Zambrano said the next day. "That's all I can say. I feel bad for that because I have to be in control of myself. I was frustrated, we had a little discussion and it went into a fight. Like I said, it's all my fault."
Here's something you probably guessed: Zambrano does not like to lose.
"He had a ping-pong table," Ortega said in an interview this spring, "and I was beating him, and I was making fun of him. He had a phone call or something, and his wife came to me, and said, 'Hector, don't do that. You'll be playing six, seven hours.' Whatever he decides to do, he will try his best to win."
National League Division Series schedule
|Wed., Oct. 3||10 p.m.||Chase Field||TBS|
|Thu., Oct. 4||10 p.m.||Chase Field||TBS|
|Sat. Oct. 6||6 p.m.||Wrigley Field||TBS|
|*Sun. Oct. 7||1 p.m.||Wrigley Field||TNT|
|*Tue. Oct. 9||10 p.m.||Chase Field||TBS|
|Wed., Oct. 3||3 p.m.||Citizens Bank Park||TBS|
|Thu., Oct. 4||3 p.m.||Citizens Bank Park||TBS|
|Sat. Oct. 6||9:30 p.m.||Coors Field||TBS|
|*Sun. Oct. 7||10 p.m.||Coors Field||TBS|
|*Tue. Oct. 9||6:30 p.m.||Citizens Bank Park||TBS|
|* If necessary. All times ET.|
The Cubs found Zambrano through Julio Figueroa, 40, a buscon, or scout, who lived in Venezuela. He first saw the excitable youngster when he was a teen and working at a gas station. But no one knew that skinny 15-year-old would win 18 games and help the Cubs advance to the postseason.
"You hear a lot of scouts project -- we're in the business of projecting," Fleita said. "Who could project an athlete of his size, who weighs close to 260, could still remain agile and hit?"
Zambrano can hit, slugging six home runs last season. He's a switch-hitter, and in the offseason, he spends as much time hitting left-handed as he does right-handed. Zambrano trains at the baseball academy in Venezuela, and would show up every day to run, hit and throw. Figueroa joked that he needed more baseballs because Big Z hits so many out of the park.
Big Z hasn't been as prolific at the plate this year, hitting "just" two homers, but showed on Friday how effective he can be on the mound. He threw seven shutout innings against the Reds, striking out four. That $91.5 million contract extension he received on Aug. 17 looks like a bargain.
"He pitched," Piniella said of Zambrano's performance against the Reds. "He didn't have a really, really good fastball, but he used his split-finger well, he had his slider going and his sinker was moving."
Watch Zambrano at the start of the game. After warmups, he gets down on one knee behind the mound to say a prayer. He's not asking for a win; it's to protect him. When he walks off the field, he will point to the sky.
"Whatever happened this season, I thank God because he was my strength and he was my power," Zambrano said.
Ortega remembers when Figueroa first approached him, and told him about the 180-pound youngster who was pitching and playing right field in Puerto Cabello, Venezuela.
"[Figueroa] said, 'I found a guy and he's very good.' He was right," Ortega said.
Figueroa can expect a phone call soon from Zambrano. The Cubs pitcher always calls him for advice.
"There are a lot of people who get to a place and forget about who helped them get started," Ortega said. "[Zambrano] calls before a game. Sometimes he calls just to make sure we're going to watch."
They'll be watching Wednesday. Zambrano did not face the Diamondbacks this season, and he's 1-2 with a 4.88 ERA in four career starts. None of that matters.
"This season is over for me," Zambrano said, "and now I'm thinking about the playoffs and trying to do a lot of things to help my team."
Carrie Muskat is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.