Jackson has had coaches across the country work with him. But when asked for the one person who was key to his rise to the big leagues, he doesn't hesitate.
Jackson wouldn't be playing Major League Baseball if not for a 22-year-old woman who died from lung cancer.
Jill Costello was one of the first people Jackson met at Berkeley. She would eventually introduce him to his girlfriend, Darby Anderson. Costello was the coxswain for the Berkeley crew team, which won the Pac 10 championship in 2010 and finished second in the national meet.
Costello never smoked cigarettes, yet was diagnosed with lung cancer when she was 21. She died on June 24, 2010, just weeks after nationals.
"I was in the Florida State League when she died," said Jackson, ranked by MLB.com as the Cubs' No. 3 prospect. "I'm out there playing, in the heat, and struggling -- I think I was hitting like .280 or something, and to me, that's not good enough.
"I was not loving being in Daytona, and she's going through this, and I wore the bracelet [in support of Costello]. I would look down at my bracelet when I was on the field, and I'm like, 'I'm so hot now, it's like 100 degrees,' and I'd say, 'This is nothing. This is nothing.' It seemed minimal compared to what she was going through."
If you don't know Costello's story, do a Google search. Go to www.jillslegacy.org. Check out the Sports Illustrated feature from November 2010. You can't read it without getting choked up.
Anderson, who was a close friend of Costello's at Berkeley, now works for the Bonnie J. Addario Lung Cancer Foundation, and runs Jill's Legacy, which organizes "Jog for Jill" fundraisers.
"Lung cancer has this stigma that you can only get it smoking cigarettes," Jackson said. "People don't find out they have lung cancer until it's too late. It happens to young people, it happens to women. It's something like 80 percent of new lung cancer patients never smoked, or quit a long time ago. It's like any other cancer. We don't know enough to know why people are getting it.
"There are all these men and women who have played important roles in my baseball career, and I want to tell people about all of them," Jackson said, sitting in the dugout at Wrigley Field. "But she continues to be a huge inspiration for me."
Costello never complained while going through her chemo treatments. Jackson, 24, won't forget her smile.
He had plenty of baseball-centric people who guided him. Start with his father, Peter.
"He wasn't just a father, he was my best friend," Jackson said. "We watched Giants games growing up, and we'd barely watch half the games because I wanted to be in the backyard playing catch."
Robertson was Jackson's baseball coach at Miramonte High School in Orinda, Calif.
"He would be the guy who was tough love," Jackson said. "I was a shortstop in high school, and if I didn't dive, I'd hear it. He was the motivator."
Zuber was the hitting coach at Berkeley; David Esquer was the head coach. Both were influential in Jackson's baseball upbringing. In three seasons, he batted .303.
He's worked his way up through the Cubs' Minor Leagues -- with more coaches along the way -- and since his promotion to the Cubs on Aug. 5, Jackson has received instruction from Sveum, hitting coach James Rowson, outfield coach Dave McKay.
"I've joined a coaching staff who couldn't be more knowledgeable, couldn't be more supportive in every aspect of my game," Jackson said. "I feel really fortunate to come into a group of people who know so much about baseball and are so willing to help me learn and help me become the player I should become.
"Without sounding arrogant, I feel I have a ton of athletic ability and a ton of talent. It's just learning how to use it all. I wouldn't say I'm raw. I've developed a lot of my skills, and there's certainly more room to grow and cultivate, and these guys have given me the opportunity to get the most out of my ability."
There's a coach on almost every team he's played with whom Jackson has connected. He'll talk about any of them.
"But when it comes down to it," he said, "I feel like it's Jill's story I want to tell. Did she influence my baseball career directly? Not at all. She didn't teach me how to hit. But she's the constant inspiration that I have."
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.Less